Bioremediation of oil by marine microbial mats

Cyanobacterial mats developing in oil-contaminated sabkhas along the African coasts of the Gulf of Suez and in the pristine Solar Lake, Sinai, were collected for laboratory studies. Samples of both mats showed efficient degradation of crude oil in the light, followed by development of an intense bloom of Phormidium spp. and Oscillatoria spp. Isolated cyanobacterial strains, however, did not degrade crude oil in axenic cultures. Strains of sulfate-reducing bacteria and aerobic heterotrophs were capable of degrading model compounds of aliphatic and aromatic hydrocarbons. Results indicate that degradation of oil was done primarily by aerobic heterotrophic bacteria. The oxygenic photosynthesis of oil-insensitive cyanobacteria supplied the molecular oxygen for the efficient aerobic metabolism of organisms, such as Marinobacter sp. The diurnal shifts in environmental conditions at the mat surface, from highly oxic conditions in the light to anaerobic sulfide-rich habitat in the dark, may allow the combined aerobic and anaerobic degradation of crude oil at the mat surface. Hence, coastal cyanobacterial mats may be used for the degradation of coastline oil spills. Oxygen microelectrodes detected a significant inhibition of photosynthetic activity subsequent to oil addition. This prevailed for a few hours and then rapidly recovered. In addition, shifts in bacterial community structure following exposure to oil were determined by denaturing gradient gel electrophoresis of PCR-amplified fractions of 16S rRNA from eubacteria, cyanobacteria and sulfate-reducing bacteria. Since the mats used for the present study were obtained from oil-contaminated environments, they were believed to be preequilibrated for petroleum remediation. The mesocosm system at Eilat provided a unique opportunity to study petroleum degradation by mats formed under different salinities (up to 21%). These mats, dominated by cyanobacteria, can serve as close analogues to the sabkhas contaminated during the Gulf War in Kuwait and Saudi Arabia. Electronic Publication     

A computer study of the evolution of aerobic heterotrophic bacterial populations in sewage and river waters

The biodegradation of six surface active agents tested. The biochemical characteristics of the aerobic heterotrophic bacteria present in Montpellier waste waters and in Rhône water, before and after degradation, were studied by a standardized microbiological method. Four hundred strains isolated from these populations were compared to 29 reference strains by computer analysis. The reference strains were first grouped in classes (single linkage). Then the strains were compared first to these classes, and then to each reference strain. Whereas the bacterial populations were widely distributed before biodegradation, after degradation they were restricted to a few prevailing genera:Pseudomonas, Alcaligenes, andKlebsiella.     

Survey of petroleum-degrading bacteria in coastal waters of Sunderban Biosphere Reserve

A survey of petroleum-degrading bacteria was carried out in the Indian part of deltaic Sunderbans to evaluate the distribution of the naturally occurring petroleum-degrading aerobic bacteria. Bacteriological analysis of surface water samples collected from five different locations in the Hooghly–Matla river mouth showed that, depending on the location, 0.08–2.0% of the heterotrophic bacteria culturable in marine agar medium could degrade crude petroleum hydrocarbons as the sole source of carbon. In the entire study area, the number of heterotrophic bacteria ranged from 1 × 10³ to 3.8 × 10⁵ c.f.u/ml, amongst which 2.7 × 10¹ to 6 × 10³ c.f.u/ml were petroleum degraders. There was a maximum number of petroleum-degrading bacteria in the waters of Haldia Port and its surrounding areas, where the water is highly polluted by hydrocarbon discharges from a nearby oil refinery and from the ships docking at the port. Among the isolates, identified on the basis of their Gram reaction, morphological and biochemical tests including the use of API20E strips, Pseudomonas, Mycobacterium, Klebsiella, Acinetobacter, Micrococcus, and Nocardia were the most common petroleum degraders. Other heterotrophic bacteria included several species of Escherichia, Klebsiella, non-oil-degrading Pseudomonas, Vibrio, Streptococcus, Staphylococcus and Bacillus. Following preliminary selection, five strains, showing best growth in medium with oil fraction as sole carbon source, were chosen for estimation of the efficiency of crude oil biodegradation. The selected strains belonged to Pseudomonas (two strains), Mycobacterium (two strains), and Nocardia (one strain). These strains degraded 47–78% of Arab-Mix crude oil over a period of 20 days. The best oil-degrading isolate, a strain of Pseudomonas aeruginosa, (BBW1), was found to degrade and multiply more rapidly in crude oil than the rest. BBW1 showed profuse growth in Bushnell Haas medium containing crude oil (as sole source of carbon) at high concentrations ranging from 0.2 to 20% (v/v), with optimum at 10%. As much as 75% of the oil was degraded within 72 h of incubation with the bacteria. Physicochemical analysis showed considerable decrease in initial boiling point and carbon residue of the degraded oil. The ability to degrade crude oil was found to be associated with a single 70-kb plasmid, pBN70. Resistance to the metals Mn²⁺ (50 mM), Mg²⁺ (200 mM), Zn²⁺ (6 mM), Ni²⁺ (10 mM) and antibiotics like ampicillin (10 g/ml), cephalexin (30 g/ml), nitrofurantoin (300 g/ml) and penicillin (10 U/ml) were plasmid-mediated.     

Degradation of Microcystin-RR by Sphingomonas sp. CBA4 isolated from San Roque reservoir (Córdoba – Argentina)

We report the aerobic biodegradation of Microcystin-RR (MC-RR) by a bacterial strain isolated from San Roque reservoir (Córdoba – Argentina). This bacterium was identified as Sphingomonas sp. (CBA4) on the basis of 16S rDNA sequencing. The isolated strain was capable of degrading completely MC-RR (200 μg l⁻¹) within 36 h. We have found evidence that MC-RR biodegradation pathway by this Sphingomonas sp. strain would start by demethylating MC-RR, affording an intermediate product, which is finally biodegraded by this strain within 72 h. Our results confirm that certain environmental bacteria, living in the same habitat as toxic cyanobacteria, have the capability to perform complete biodegradation of MC, leading to natural bioremediation of waterbodies. The bacterium reported here presents genetic homologies with other strains that degrade MC-LR. However, initial demethylation of MC-RR has been not described previously, raising questions on the probable presence of different biodegradation pathways for different MC variants.     

Construction of cyanobacterial-bacterial consortium on the basis of axenic cyanobacterial cultures and heterotrophic bacteria cultures for bioremediation of oil-contaminated soils and water ponds

The ways of the creation of cyanobacterial-bacterial communities with a high remediation potential for cleaning of oil-contaminated soils and water reservoirs are considered. A special methodology was elaborated for the obtaining of bacteriologically pure (axenic) cultures of cyanobacteria: Phormidium sp. K-1, Oscillatoria sp. A-2, and Oscillatoria sp. C-3. It was shown that 14 strains of bacteria associated with these cyanobacteria manifest a hydrocarbon-oxidizing activity. They belong to the genera Pseudomonas, Alcaligenes, Arthrobacter, and Bacillus. The usage of oil-degrading bacteria, which we isolated from water reservoirs or took from collections, allowed us to construct artificial cyanobacterial-bacterial communities with a high hydrocarbon-oxidizing activity. In field experiments on the landfill site Khimpromservis Aktobe, the high remediatory effect of cyanobacterial-bacterial associations between Phormidium sp. K-1 sp. and bacteria Pseudomonas stutzeri A1, Pseudomonas sp. N2, and P. alcaligenes A5 was demonstrated. The results obtained are the basis for the elaboration of microbiological technologies of environment protection using cyanobacteria.     

The Effects of Cyanobacterial Exudates on Bacterial Growth and Biodegradation of Organic Contaminants

The pulp and paper industry largely depends on the biodegradation activities of heterotrophic bacteria to remove organic contaminants in wastewater prior to discharge. Our recent discovery of extensive cyanobacterial communities in pulp and paper waste treatment systems led us to investigate the potential impacts of cyanobacterial exudates on growth and biodegradation efficiency of three bacterial heterotrophs. Each of the three assessed bacteria represented different taxa commonly found in pulp and paper waste treatment systems: a fluorescent Pseudomonad, an Ancylobacter aquaticus strain, and a Ralstonia eutropha strain. They were capable of utilizing phenol, dichloroacetate (DCA), or 2,4-dichlorophenoxyacetic acid (2,4-D), respectively. Exudates from all 12 cyanobacterial strains studied supported the growth of each bacterial strain to varying degrees. Maximum biomass of two bacterial strains positively correlated with the total organic carbon content of exudate treatments. The combined availability of exudate and a known growth substrate (i.e., phenol, DCA, or 2,4-D) generally had a synergistic affect on the growth of the Ancylobacter strain, whereas mixed effects were seen on the other two strains. Exudates from four representative cyanobacterial strains were assessed for their impacts on phenol and DCA biodegradation by the Pseudomonas and Ancylobacter strains, respectively. Exudates from three of the four cyanobacterial taxa repressed phenol biodegradation, but enhanced DCA biodegradation. These dissimilar impacts of cyanobacterial exudates on bacterial degradation of contaminants suggest a species-specific association, as well as a significant role for cyanobacteria during the biological treatment of wastewaters.     

Characterization of Ligninolytic Bacteria and Analysis of Alkali-Lignin Biodegradation Products

Ligninolytic bacteria degrading lignin were isolates and identified, and their biodegradation mechanism of alkaline-lignin was investigated. Four strains with lignin degradation capability were screened and identified from the soil, straw, and silage based on their decolorizing capacity of aniline blue and colony size on alkaline-lignin medium. The degradation ratio of Bacillus aryabhattai BY5, Acinetobacter johnsonii LN2, Acinetobacter lwoffii LN4, and Micrococcus yunnanensis CL32 have been assayed using alkaline-lignin as the unique carbon source. Further, the Lip (lignin peroxidase) and Mnp (manganese peroxidase) activities of strains were investigated. Lip activity of A. lwoffii LN4 was highest after 72 h of incubation and reached 7151.7 U · l^–1. Mnp activity of M. yunnanensis CL32 was highest after 48 h and reached 12533 U · l^–1. The analysis of alkaline-lignin degradation products by GC-MS revealed that the strains screened could utilize aromatic esters compounds such as dibutyl phthalate (DBP), and decomposite monocyclic aromatic compounds through the DBP aerobic metabolic pathway. The results indicate that B. aryabhattai BY5, A. johnsonii LN2, A. lwoffii LN4, and M. yunnanensis CL32 have high potential to degrade alkaline-lignin, and might utilize aromatic compounds by DBP aerobic metabolic pathway in the process of lignin degradation.Key words: isolation, bacteria, alkali-lignin, biodegradation products     

Role of Predatory Bacteria in the Termination of a Cyanobacterial Bloom

Changes in cyanobacterial abundance and in the occurrence of bacteria of bacteria capable of lysing cyanobacteria were monitored over a period of 6 months (May to October 1998) in eutrophic Brome Lake (Quebec, Canada), in which dense cyanobacterial blooms recur regularly. By screening lake water, we isolated two strains of lytic bacteria, from the family Cytophagaceae. When tested on 12 cyanobacteria and 6 heterotrophic bacteria, strain 1 lysed only Anabaena flos-aquae and strain 2 lysed only Synechococcus cedorum, Synechococcus leopoliensis, Synechococcus elongatus, and Anacystic nidulans: both liquid and agar-grown cultures of these cyanobacteria were lysed. The number of plaque forming units of bacteria increased dramatically during the decline of the bloom. The results are consistent with an important role for these host-specific lytic bacteria in control and elimination of cyanobacterial blooms in this lake.     

Two New Mycobacterium Strains and Their Role in Toluene Degradation in a Contaminated Stream

Two toluene-degrading strains, T103 and T104, were isolated from rock surface biomass in a freshwater stream contaminated with toluene. The strains exhibit different capacities for degradation of toluene and other aromatic compounds and have characteristics of the genus Mycobacterium. Both are aerobic, rod-shaped, gram-positive, nonmotile, and acid-alcohol fast and produce yellow pigments. They have mainly straight-chain saturated and monounsaturated fatty acids with 10 to 20 carbon atoms and large amounts of tuberculostearic acid that are typical of mycobacteria. Fatty acid analyses indicate that T103 and T104 are different mycobacterial strains that are related at the subspecies level. Their identical 16S rDNA sequences are most similar to Mycobacterium aurum and Mycobacterium komossense, and they constitute a new species of fast-growing mycobacteria. Ecological studies reveal that toluene contamination has enriched for toluene-degrading bacteria in the epilithic microbial community. Strains T103 and T104 play only a small role in toluene degradation in the stream, although they are present in the habitat and can degrade toluene. Other microorganisms are consequently implicated in the biodegradation.     

Diversity of Heterotrophic Halophilic Bacteria Isolated from Coastal Solar Salterns,Bulgaria and Their Ability to Synthesize Bioactive Molecules with Biotechnological Impact

Investigations on the microbial life in several coastal solar salterns have revealed the presence of novel organisms and synthesis of unusual molecules active in extreme conditions which might be useful in different biotechnological industries. Biodiversity of heterotrophic aerobic bacteria isolated from two salterns, Pomorie salterns and Burgas salterns located at Burgas Bay, Black Sea coast, Bulgaria, as well as ability of the isolates to synthesize biotechnologically valuable compounds were investigated. The results revealed high taxonomic and metabolic bacterial diversity—we isolated 20 morphologically different moderately halophilic and two halotolerant strains affiliated with 11 species from eight genera referred to the phyla Proteobacteria, Firmicutes, and Actinobacteria. Gram-negative bacteria belonged to the genera Halomonas, Chromohalobacter, Salinivibrio, Cobetia, and Nesiotobacter, and gram-positive strains were representatives of the genera Virgibacillus, Salinicoccus, and Brevibacterium. All isolates were found to be alkalitolerant, and 41% of them were psychrotolerant. The strains degraded nine of the tested 18 substrates; polygalacturonase, catalase, phytase, and lipase producers were predominant. This is the first reported detection of xanthan lyase, gellan lyase, arabinase, and phytase activities in halophilic bacteria. Nine of the strains belonging to five different genera were found to produce exopolysaccharides (EPS). The highest level of EPS was observed in Chromohalobacter canadensis strain 28. More than a half of the strains displayed antimicrobial activity against one to five test bacteria and yeasts. The present study is the first report on halophilic bacteria isolated from salterns at the Black Sea coast indicating that the investigated area is an untapped resource of halophilic bacteria with biotechnological potential.     

Phylogenetic relationships of nonaxenic filamentous cyanobacterial strains based on 16S rRNA sequence analysis

In order to determine the nearly complete 16S rRNA gene sequences of cyanobacteria originating from nonaxenic cultures, a cyanobacterium-specific oligonucleotide probe was developed to distinguish polymerase chain reaction (PCR) products of the cyanobacterial rRNA operons from those resulting from amplification of contaminating bacteria. Using this screening method the 16S rRNA genes of four nonaxenic filamentous cyanobacterial strains belonging to the generaLeptolyngbya andOscillatoria were cloned and sequenced. For the genusLeptolyngbya, the 16S rRNA sequence of the axenic strain PCC 73110 was also determined. Phylogenetic trees were constructed based on complete and partial sequences. The results show that the strainsLeptolyngbya foveolarum Komárek 1964/112,Leptolyngbya sp. VRUC 135 Albertano 1985/1, andLeptolyngbya boryanum PCC 73110 belong to the same cluster. StrainOscillatoria cf.corallinae SAG 8.92, which contains the rare photosynthetic pigment CU-phycoerythrin, is not closely related to other CU-phycoerythrin-containing cyanobacteria.Oscillatoria agardhii CYA 18, which is a representative of planktonicOscillatoria species that form toxic blooms in Norwegian inland waters, has no close relatives in the tree.     

The use of yeast for microbial degradation of some selected mycotoxins

Several biodegradation experiments were carried out using 10 different yeast strains.Saccharomyces spp., Kluyveromyces spp. andRhodotorula spp. were tested for biodegradation of selected mycotoxins (ochratoxin A, nivalenol, deoxynivalenol and fumonisin B₁) standardsin vitro. There was confirmed that some yeast strains are able to degrade some mycotoxins. However, great differences between individual strains were observed. Moreover, 12Saccharomyces cerevisiae strains were tested for their potential capability to degrade zearalenone and fumonisins in Sabouraud broth. Two strains were capable to degrade zearalenone totally, one strain decreased the mycotoxin concentration up to 25%, and one strain up to 75% of original amount. Two strains were capable to degrade fumonisins partially.     

Ecology, physiology, and phylogeny of deep subsurface Sphingomonas sp

Several new species of the genus Sphingomonas including S. aromaticivorans, S. stygia, and S. subterranea that have the capacity for degrading a broad range of aromatic compounds including toluene, naphthalene, xylenes, p-cresol, fluorene, biphenyl, and dibenzothiophene, were isolated from deeply-buried (>200 m) sediments of the US Atlantic coastal plain (ACP). In S. aromaticivorans F199, many of the genes involved in the catabolism of these aromatic compounds are encoded on a 184-kb conjugative plasmid; some of the genes involved in aromatic catabolism are plasmid-encoded in the other strains as well. Members of the genus Sphingomonas were common among aerobic heterotrophic bacteria cultured from ACP sediments and have been detected in deep subsurface environments elsewhere. The major source of organic carbon for heterotrophic metabolism in ACP deep aquifers is lignite that originated from plant material buried with the sediments. We speculate that the ability of the subsurface Sphingomonas strains to degrade a wide array of aromatic compounds represents an adaptation for utilization of sedimentary lignite. These and related subsurface Sphingomonas spp may play an important role in the transformation of sedimentary organic carbon in the aerobic and microaerobic regions of the deep aquifers of the ACP. Received 12 May 1999/ Accepted in revised form 25 July 1999     

Degradation of a Mixture of Hydrocarbons,Gasoline, and Diesel Oil Additives by Rhodococcus aetherivorans and Rhodococcus wratislaviensis

Two strains, identified as Rhodococcus wratislaviensis IFP 2016 and Rhodococcus aetherivorans IFP 2017, were isolated from a microbial consortium that degraded 15 petroleum compounds or additives when provided in a mixture containing 16 compounds (benzene, toluene, ethylbenzene, m-xylene, p-xylene, o-xylene, octane, hexadecane, 2,2,4-trimethylpentane [isooctane], cyclohexane, cyclohexanol, naphthalene, methyl tert-butyl ether [MTBE], ethyl tert-butyl ether [ETBE], tert-butyl alcohol [TBA], and 2-ethylhexyl nitrate [2-EHN]). The strains had broad degradation capacities toward the compounds, including the more recalcitrant ones, MTBE, ETBE, isooctane, cyclohexane, and 2-EHN. R. wratislaviensis IFP 2016 degraded and mineralized to different extents 11 of the compounds when provided individually, sometimes requiring 2,2,4,4,6,8,8-heptamethylnonane (HMN) as a cosolvent. R. aetherivorans IFP 2017 degraded a reduced spectrum of substrates. The coculture of the two strains degraded completely 13 compounds, isooctane and 2-EHN were partially degraded (30% and 73%, respectively), and only TBA was not degraded. Significant MTBE and ETBE degradation rates, 14.3 and 116.1 μmol of ether degraded h⁻¹ g⁻¹ (dry weight), respectively, were measured for R. aetherivorans IFP 2017. The presence of benzene, toluene, ethylbenzene, and xylenes (BTEXs) had a detrimental effect on ETBE and MTBE biodegradation, whereas octane had a positive effect on the MTBE biodegradation by R. wratislaviensis IFP 2016. BTEXs had either beneficial or detrimental effects on their own degradation by R. wratislaviensis IFP 2016. Potential genes involved in hydrocarbon degradation in the two strains were identified and partially sequenced.The pollution of soils by petroleum compounds is of great concern mainly because of the solubilities of the different molecules in water, which can endanger aquifers in contact with polluted zones. Petroleum storage facilities are frequently the source of pollution due to leaks and spills during fuel transfer and storage. For example, in the United States in 2007, the EPA indicated that nearly 110,000 old leaks have not yet been cleaned up, and there are an unknown number of petroleum brownfield sites (estimated to be over 200,000) that are predominately old abandoned gas stations (http://www.epa.gov/OUST/pubs/OUST_FY07_Annual_Report-_Final_4-08.pdf). In these locations, the contamination can be generated by diesel oil and/or gasoline leaks from storage tanks, resulting in a complex mixture of compounds with different water solubilities and different biodegradabilities. Among all the phenomena occurring at polluted sites, (i) the interactions between the different compounds can result in enhanced solubility for low-solubility compounds, (ii) the differences in biodegradability levels between the dissolved molecules can lead to dispersion of the poorly biodegradable or nonbiodegradable compounds, and (iii) in the presence of mixtures of compounds, interactions between some of them can lead to detrimental or beneficial effects. For example, methyl tert-butyl ether [MTBE] could enhance the mobility of dissolved benzene, toluene, ethylbenzene, and xylenes [BTEXs] by exerting a cosolvent effect that decreases sorption-related retardation (30). The impact of additive use after petroleum refining to meet specific requirements is a point that deserves more study. MTBE was used extensively in the United States and elsewhere in the world. Several states banned the use of MTBE because of numerous reports of groundwater pollution, but this compound is still used in Europe. Although its use is decreasing, it still remains high, and by the end of 2007, global MTBE production was about 15 million tons. Ethyl tert-butyl ether (ETBE) is used in Europe (France, Spain, Belgium, and Germany), with European production reaching 626,300 tons in 2004 (http://www.agriculture.total.fr). MTBE and ETBE can be added at up to 15% to gasoline in order to reach the octane index requirement; their use was shown to limit noncombusted hydrocarbon release in exhaust pipe fumes. 2-Ethylhexyl nitrate (2-EHN) is the nitric ester of 2-ethyl-1-hexanol, and it is added to diesel formulations at up to 0.4%. The 2-EHN market is about 100,000 tons/year. Alkylates are native components of petroleum products, but in view of the use of ethanol in gasoline, alkylates, like 2,2,4-trimethylpentane (isooctane), are among the few high-octane alternatives that have been proposed, if only the minimal volume of ethanol required to meet oxygenate requirements are used in reformulated gasoline. In this case, other fuel constituents would be needed to make up the resulting 5% gap and the octane shortfall of about 1.5 octane points. Isooctane has an octane rating of 100 and would be attractive for refiners as an octane enhancer since it can be produced by former MTBE production plants (35).Data concerning the use of additives have to be taken into account to assess the impact of petroleum products on polluted sites, such as gas stations, where leaks from different storage tanks can occur, leading to contamination by complex mixtures of petroleum products. The biodegradation of monoaromatic (BTEX) compounds and alkanes has been studied extensively, and both are generally quite biodegradable under aerobic conditions (44, 46). Regarding the biodegradability of MTBE, several microorganisms have been isolated with specific degradation capacities, and some of the genes involved in the biodegradation pathway have been characterized (28). The first-order attenuation rates for MTBE in the plumes in which biodegradation occurred varied from 0.56 to 4.3 year⁻¹, a rate of biodegradation not sufficient to contain the plume (7). In addition, there are numerous sites for which no biodegradation was observed (3, 10), and the presence of BTEXs and MTBE has been shown in the case of Methylibium petroleiphilum PM1 to delay the onset of MTBE biodegradation (13).The behavior of ETBE when spilled in the environment has not been as well studied as that of MTBE, and the extent of contamination has not been documented sufficiently. Similar to that of MTBE, the biodegradation of ETBE is not always observed in microcosms with soils or aquifers derived from contaminated sites (3). Microorganisms able to grow on ETBE have been isolated, and the first monooxygenase system able to degrade ETBE was identified as a cytochrome P450 monooxygenase (encoded by the ethRABCD genes) in Rhodococcus ruber IFP 2001 (6, 21). Highly similar eth gene clusters were also isolated from Rhodococcus zopfii IFP 2005 and Gordonia sp. strain IFP 2009 (4, 16). R. ruber IFP 2001, R. zopfii IFP 2005, and Gordonia sp. strain IFP 2009 were able to grow on ETBE at the expense of the C₂ moiety being released by the cleavage of the ether bond with the accumulation of tert-butyl alcohol (TBA) in the growth culture (C. Malandain, F. Fayolle-Guichard, and T. Vogel, submitted for publication). Interestingly, other microorganisms belonging to the genus Rhodococcus were reported to have biodegradation capacities toward ether fuels. Mo et al. (31) isolated a Rhodococcus sp. strain able to degrade MTBE to a low extent; R. aetherivorans, a new species that belongs to MTBE-degrading actinomycetes (20) was characterized, but the enzymatic system responsible for the MTBE oxidation was not elucidated; Rhodococcus sp. strain EH831 was able to degrade MTBE (27).There are few data in the literature regarding the biodegradability of isooctane; Mycobacterium austroafricanum IFP 2173 was the only strain described for its ability to use isooctane as the sole carbon and energy source (42), and more recently, Cho et al. (9) demonstrated the biodegradability of isooctane using previously acclimated biomass. Regarding the biodegradability of 2-EHN, only M. austroafricanum IFP 2173 was recently reported to degrade 2-EHN to 4-ethyldihydrofuran-2(3H)-one (36).The biodegradation of complex mixtures of hydrocarbons has generally been studied only under the highest-performing conditions using different processes (e.g., biofilters) in which the microorganisms and the role played by each of them have not necessarily been elucidated. Individual microorganisms have generally been characterized for their ability to degrade individual petroleum compounds or classes of compounds, i.e., monoaromatics. There is much less work addressing the issue of the biodegradation by individual, characterized microorganisms of complex mixtures generally found in sites polluted by hydrocarbons, even though some bacterial genera (Pseudomonas and Rhodococcus, for example) are known to degrade a wide range of xenobiotics (17, 25, 41). Some authors have investigated the range of biodegradation capacities of given individual strains. Solano-Serena et al. (42) previously isolated M. austroafricanum IFP 2173 from gasoline-contaminated groundwater, and this strain, tested on a mixture of petroleum compounds, showed extended biodegradation capacities toward various hydrocarbons. More recently, Rhodococcus sp. strain EC1 was shown to degrade BTEXs, short-chain alkanes, pyrene, and MTBE (26).The selection and the study of strains with capacities to use a broad spectrum of various hydrocarbons is of great interest because it could facilitate the study of the effect of selective pressure in terms of gene acquisition. From a bacterial consortium, including bacteria from soil at a gas station polluted by leaking tanks and enriched on a mixture of various hydrocarbons, we isolated two strains of Rhodococcus wratislaviensis and Rhodococcus aetherivorans and studied their biodegradation capacities toward hydrocarbons or additives added individually or in mixtures.     

The new alkaliphilic bacteriochlorophyll <Emphasis Type="Italic">a</Emphasis>-containing bacterium <Emphasis Type="Italic">Roseinatronobacter monicus</Emphasis> sp. nov. from the hypersaline Soda Mono Lake (California,United States)

Two strains of pink-colored aerobic bacteriochlorophyll a-containing bacteria were isolated from aerobic (strain ROS 10) and anaerobic (strain ROS 35) zones of the water column of Mono Lake (California, United States). Cells of the bacteria were nonmotile oval gram-negative rods multiplying by binary fission by means of a constriction. No intracellular membranes were detected. Polyphosphates and poly-β-hydroxybutyric acid were the storage compounds. Pigments were represented by bacteriochlorophyll a and carotenoids of the spheroidene series. The strains were obligately aerobic, mesophilic (temperature optimum of 25–30°C), alkaliphilic (pH optimum of 8.5–9.5), and moderately halophilic (optimal NaCl concentration of 40 g/l). They were obligately heterotrophic and grew aerobically in the dark and in the light. Respiration was inhibited by light at wavelengths corresponding to the absorption of the cellular pigments. The substrate utilization spectra were strain-specific. In the course of organotrophic growth, the bacteria could oxidize thiosulfate to sulfate; sulfide and polysulfide could also be oxidized. The DNA G+C content was 59.4 mol % in strain ROS 10 and 59 mol % in strain ROS 35. In their phenotypic properties, the new strains were close but not identical to the alkaliphilic bacterium Roseinatronobacter thiooxidans. The distinctions in the nucleotide sequences of the 16S rRNA genes (2%) and low DNA-DNA hybridization level with Rna. thiooxidans (22–25%) allow the new strains to be assigned to a new species of the genus Roseinatronobacter, Roseinatronobacter monicus sp. nov. with the type strain ROS 35^T (=UNIQEM U-251^T = VKM B-2404^T).     

Low-molecular mass carbohydrate accumulation in cyanobacteria from a marine microbial mat in response to salt

Forty seven strains of cyanobacteria, all isolated from microbial mats of intertidal sediments of the island of Mellum (North Sea), were analyzed for the presence of organic osmotica. The cyanobacteria examined belonged to taxonomically different groups and were classified according to their salt optimum and salt tolerance as either freshwater, brackish or marine. Except betaine, all organic osmotica known to occur in cyanobacteria, were found. The results showed no clear correlation between the chemical nature of the organic solute and the salt optimum or salt tolerance of the cyanobacteria examined, indicating that these solutes are not specific to this marine habitat. All strains belonging to the Nostoc/Anabea-group accumulated sucrose as the sole organic osmoticum. The marine, heterocystous Calothrix sp. accumulated trehalose. All strains of the LPP-group (Lyngbya, Plectonema, Phormidium) accumulated glucosylglycerol as sole or primary organic solute. Some LPP-strains accumulated a disaccharide as a secundary solute, e.g. sucrose or trehalose. Gloeocapsa, Synechocystis and Spirulina accumulated glucosylglycerol. Two marine Oscillatoria accumulated trehalose, whereas a freshwater Oscillatoria with a broad salinity tolerance, accumulated sucrose.Analysis of field samples of the microbial mats demonstrated the presence of glycerol, glucosylglycerol, sucrose and trehalose. The relative abundance of the different compounds was related to the species composition as could be predicted from laboratory observations. These data suggest that these carbohydrates have a function in maintaining osmotic balance in the organisms within the microbial mat.     

Acidocella aromatica sp. nov.: an acidophilic heterotrophic alphaproteobacterium with unusual phenotypic traits

Three obligately heterotrophic bacterial isolates were identified as strains of a proposed novel species of extremely acidophilic, mesophilic Alphaproteobacteria, Acidocella aromatica. They utilized a restricted range of organic substrates, which included fructose (but none of the other monosaccharides tested), acetate and several aromatic compounds (benzoate, benzyl alcohol and phenol). No growth was obtained on complex organic substrates, such as yeast extract and tryptone. Tolerance of the proposed type strain of the species (PFBC) to acetic acid was much greater than that typically reported for acidophiles. The bacteria grew aerobically, and catalyzed the dissimilatory reductive dissolution of the ferric iron mineral schwertmannite under both micro-aerobic and anaerobic conditions. Strain PFBC did not grow anaerobically via ferric iron respiration, though it has been reported to grow in co-culture with acid-tolerant sulfidogenic bacteria under strictly anoxic conditions. Tolerance of strains of Acidocella aromatica to nickel were about two orders of magnitude greater than those of other Acidocella spp., though similar levels of tolerance to other metals tested was observed. The use of this novel acidophile in solid media designed to promote the isolation and growth of other (aerobic and anaerobic) acidophilic heterotrophs is discussed.     

Distribution of Aerobic Bacteria Which Contain Bacteriochlorophyll a

Sixteen strains of aerobic bacteria which contain bacteriochlorophyll a were isolated from the samples collected in aerobic marine environments: thalli of Enteromorpha linza, Porphyra sp., Sargussum horneri; beach sand; and the surface seawater from Aburatsubo Inlet. When they occurred, their proportions among the aerobic heterotrophic populations ranged from 0.9 to 1.1% in the seaweed samples and from 1.2 to 6.3% in the beach sand samples and were 0.9% in the seawater sample. The results suggested that the aerobic photopigmented bacteria widely inhabit aerobic marine environments.     

Jania rubens-associated bacteria: molecular identification and antimicrobial activity

Marine macroalgae surfaces constitute suitable substrata for bacterial colonization which are known to produce bioactive compounds. Thus, hereby we focused on heterotrophic aerobic bacteria species associated with coralline red alga Jania rubens (northern coast of Tunisia, southern Mediterranean Sea) and their inhibition against several microbial marine and terrestrial species. The whole collection (19 isolates, J1 to J19) was identified, based on their 16S ribosomal RNA gene sequences as Proteobacteria (14 strains), Bacteroidetes (4 strains) and Firmicutes (1 strain). Thirty-six percent of the isolates (J2, J9, J11, J13, J16, J17 and J18) were antibiotic-like producers with in vitro inhibition against Gram + and Gram ? bacteria and the yeast Candida albicans. Highest level of inhibition was revealed for the isolates J2, J9 and J13 identified respectively as Bacillus, Aquimarina and Pseudomonas, with strong activity against Staphylococcus aureus, Micrococcus and C. albicans, with inhibition diameters of 25 to 35 mm shown by drop test assay on T soy agar plates. Furthermore, we tested inhibition of J. rubens crude organic extracts against human and marine bacteria as well as against all J. rubens isolates, in order to determine the degree of affinity of the epibionts to their proper host. The recovery of strains with antimicrobial activity suggests that J. rubens represent an ecological niche which harbors a specific microbial diversity worthy of further secondary metabolites investigation.     

Effects of biosurfactants produced by Candida antarctica on the biodegradation of petroleum compounds

The effects of biosurfactants on the biodegradation of petroleum compounds were investigated. Candida antarctica T-34 could produce extracellular biosurfactant mannosylerythritol lipids (MELs) when it was cultured in vegetable oil. In addition, in our previous study, it was found that this strain could also produce a new type of biosurfactant while it grew on n-undecane (C₁₁H₂₄), and the biosurfactant was named as BS-UC. In flask culture of Candida antarctica, the addition of BS-UC could improve the biodegradation rate of some n-alkanes (e.g. 90.2% for n-decane, 90.2% for n-undecane, 89.0% for dodecane), a mixture of n-alkanes (82.3%) and kerosene (72.5%). By comparing the effects of the biosurfactants BS-UC and MEL and chemical surfactants on the biodegradation of crude oil, it was found that biosurfactants could be used to enhance the degradation of petroleum compounds instead of chemical surfactants. In a laboratory scale immobilized bioreactor, the addition of biosurfactant improved not only the emulsification of kerosene in simulated wastewater but also its biodegradation rate. The highest degradation rate of kerosene by addition of MEL and BS-UC reached 87 and 90% at 15 h, respectively. The results showed that the biosurfactant BS-UC was highly promising for work on biodegradation of hydrophobic contaminants.