Abundance of Three Bacterial Populations in Selected Streams

The population sizes of three bacterial species, Acinetobacter calcoaceticus, Burkholderia cepacia, and Pseudomonas putida, were examined in water and sediment from nine streams in different parts of the United States using fluorescent in situ hybridization (FISH). Population sizes were determined from three sites (upstream, midstream, and downstream) in each stream to compare differences in the occurrence and distribution of the species within each stream and among streams. Physical and chemical variables measured reflected differences in environmental conditions among the streams. In the water, B. cepacia numbers were highest in the agricultural, Iowa stream. P. putida numbers were highest in the southern coastal plain streams, Black Creek (GA) and Meyers Branch (SC). Compared to the other two species, the abundance of A. calcoaceticus was similar in all the streams. In sediment, the greatest abundance of all three species was found in the Iowa stream, while the lowest was in Hugh White Creek (NC). Detrended correspondence analysis (DCA) explained 95.8% and 83.9% of the total variation in bacterial numbers in water and sediment of the streams, respectively. In sediments and water, B. cepacia numbers were related to nitrate concentrations. A. calcoaceticus in water clustered with several environmental variables (i.e., SRP, pH, and conductivity) but benthic populations were less well correlated with these variables. This study reveals the potential influence of various environmental conditions on different bacterial populations in stream communities.     

Culturability of Stream Bacteria Assessed at the Assemblage and Population Levels

Lotic bacterial communities can be examined at multiple levels: from the assemblage level to populations of individual species. In stream environments, as in many other systems, the percentage of bacteria that are culturable is quite low. In this study, the culturability of the overall bacterial assemblage, as well as the culturability of three common species (Acinetobacter calcoaceticus, Burkholderia cepacia, and Pseudomonas putida), was determined in samples collected from four streams on three dates. Colony hybridization (colonies were grown on modified nutrient agar) and fluorescent in situ hybridization were used to calculate the percentage of cells of a given species that were culturable. Approximately half of the overall assemblage was estimated to be viable but nonculturable cells (VBNC). The culturability of two of the species was low (0.29% for A. calcoaceticus and 0.46% for P. putida), whereas the value for B. cepacia (2.48%) exceeded the overall assemblage level culturability (0.90%). Overall, both bacterial assemblages and populations were dominated by VBNC. These results show quantitatively that not all members of a species that has culturable representatives are culturable when retrieved from natural populations, likely because of interspecific phenotypic and genotypic variability. Thus, the large pool of nonculturable cells includes representatives of species that are, under some circumstances, culturable.     

Response of Biofilm Bacteria to Dissolved Organic Matter from Decomposing Maple Leaves

Stream bacteria play an important role in the utilization of dissolved organic matter (DOM) leached from leaves, and in transfer of this DOM to other trophic levels. Leaf leachate is a mixture of labile, recalcitrant, and inhibitory compounds, and bacterial communities vary in their ability to utilize leachate. The purpose of this study was to determine the effects of DOM from sugar maple leaves on bacterial populations in biofilms on decomposing leaf surfaces. Populations of Acinetobacter calcoaceticus, Burkholderia cepacia, and Pseudomonas putida were enumerated on decomposing maple leaves in a northeast Ohio stream using fluorescence in situ hybridization. Additionally, artificial substrata consisting of PVC-end caps filled with agar supplemented with leaf leachate and covered with cellulose filters were used to determine bacterial response to leachate from leaves at different stages of decomposition. Population sizes of bacterial species exhibited different responses. Leachate did not affect A. calcoaceticus. B. cepacia was tolerant of phenolic compounds released from leaves and the population size increased when DOM concentrations were greatest. In contrast, P. putida was inhibited by phenolic components of leachate when total DOM concentrations were greatest. Differences in response of the bacterial species to components of leaf leachate indicate the complexity of microbial population dynamics and interactions with DOM. Differences among species in response to DOM have the potential to influence transport and retention of organic matter in stream ecosystems.     

Longitudinal changes in the benthic bacterial community of the Mahoning River (Ohio, U.S.A.)

To examine spatial differences in bacterial communities along the Mahoning River in Northeast Ohio (USA), sediment samples were collected on two dates from three sites. Downstream portions (sites 2 and 3, in this study) of the Mahoning River have been highly impacted by human activities. Two approaches were used to characterize the bacterial community: fluorescent in situ hybridization (FISH) with taxon specific probes and denaturing gradient gel electrophoresis (DGGE). Bacterial numbers (per g ash free dry mass), based on staining with DAPI (4′, 6-diamidino-2-phenylindole) or FISH with Domain Bacteria, Acinetobacter calcoaceticus or Pseudomonas putida-specific probes, were higher at the most upstream site (site 1) compared to the more disturbed downstream sites (sites 2 and 3). In addition, the number of bands based on DGGE was higher at the upstream site (site 1) compared to the two downstream sites (2 and 3) during spring. However, in summer, the number of bands was similar among sites and the most upstream (1) and the middle site (2) had the same average number of bands. In spring, the percent similarity (based on the presence/absence of bands) among the three sites was relatively low compared to summer. In general, differences in the bacterial community were found among the sites with differing levels of anthropogenic disturbance but varied between the two dates examined.     

The influence of stream sediment particle size on bacterial abundance and community composition

Sediment features may play a major role in determining benthic bacterial community structure. In this study, sediment samples were collected on four dates over the course of a year from a Northeast Ohio stream and fractionated into different particle size classes. Abundance of bacteria of various taxa on differentially sized sediment fractions was determined using fluorescent in situ hybridization which relies on taxon-specific oligonucleotide probes that hybridize to rRNA in intact cells. The differences among the size classes were generally small in comparison to the large seasonal changes observed. These seasonal changes differed greatly among taxa; for some, peaks in the number of cells hybridizing a particular probe were in the spring (Domain Bacteria, α-Proteobacteria), while others peaked in the summer/fall (γ-Proteobacteria and the Cytophaga-Flavobacterium). At the species level, the abundances of Burkholderia cepacia and Acinetobacter calcoaceticus were highest in the summer on sediments of all sizes. Seasonal differences appeared to be more of a factor driving community differences than sediment particle size.     

Ecological Significance of Microdiversity: Coexistence Among Casing Soil Bacterial Strains Through Allocation of Nutritional Resource

A combination of cultivation-based methods with a molecular biological approach was employed to investigate whether bacteria with identical 16S rRNA gene sequences can represent distinct eco- and genotypes. A set of eight bacterial strains wherein three were Pseudomonas putida and rest were Acinetobacter calcoaceticus, were isolated from casing soils community by conventional plating. These strains had identical 16S rRNA gene sequences and represented the dominant phylotype in the plateable fraction. Each strain utilized a specific combination of 154 carbon substrates, and the niche overlap indices were low, suggesting that each strain occupied a different ecological niche. Our results have implications for assessment of the diversity and biogeography of bacteria and increase the perception of natural diversity beyond the level of 16S rRNA gene sequences. It is worthwhile approach to explore prokaryotic diversity in different ecological niches.     

Relating MEC population dynamics to anode performance from DGGE and electrical data

The microbial electrolysis cell (MEC) is a promising system for H₂ production, but little is known about the active microbial population in MEC systems. Therefore, the microbial community of five different MEC graphite felt anodes was analyzed using denaturing gradient gel electrophoresis (DGGE) profiling. The results showed that the bacterial population was very diverse and there were substantial differences between microorganisms in anolyte and anode samples. The archaeal population in the anolyte and at the anodes, and between the different MEC anodes, was very similar. SEM and FISH imaging showed that Archaea were mainly present in the spaces between the electrode fibers and Bacteria were present at the fiber surface, which suggested that Bacteria were the main microorganisms involved in MEC electrochemical activity. Redundancy analysis (RDA) and QR factorization-based estimation (QRE) were used to link the composition of the bacterial community to electrochemical performance of the MEC. The operational mode of the MECs and their consequent effects on current density and anode resistance on the populations were significant. The results showed that the community composition was most strongly correlated with current density. The DGGE band mostly correlated with current represented a Clostridium sticklandii strain, suggesting that this species had a major role in current from acetate generation at the MEC anodes. The combination of RDA and QRE seemed especially promising for obtaining an insight into the part of the microbial population actively involved in electrode interaction in the MEC.     

Electing a candidate: a speculative history of the bacterial phylum OP10

In 1998, a cultivation‐independent survey of the microbial community in Obsidian Pool, Yellowstone National Park, detected 12 new phyla within the Domain Bacteria. These were dubbed ‘candidate divisions’ OP1 to OP12. Since that time the OP10 candidate division has been commonly detected in various environments, usually as part of the rare biosphere, but occasionally as a predominant community component. Based on 16S rRNA gene phylogeny, OP10 comprises at least 12 class‐level subdivisions. However, despite this broad ecological and evolutionary diversity, all OP10 bacteria have eluded cultivation until recently. In 2011, two reference species of OP10 were taxonomically validated, removing the phylum from its ‘candidate’ status. Construction of a highly resolved phylogeny based on 29 universally conserved genes verifies its standing as a unique bacterial phylum. In the following paper we summarize what is known and what is suspected about the newest described bacterial phylum, the Armatimonadetes.     

Nutrients and Other Abiotic Factors Affecting Bacterial Communities in an Ohio River (USA)

Nitrogen and phosphorus additions from anthropogenic sources can alter the nutrient pool of aquatic systems, both through increased nutrient concentrations and changes in stoichiometry. Because bacteria are important in nutrient cycling and aquatic food webs, information about how nutrients affect bacterial communities enhances our understanding of how changes in nutrient concentrations and stoichiometry potentially affect aquatic ecosystems as a whole. In this study, bacterial communities were examined in biofilms from cobbles collected across seasons at three sites along the Mahoning River (Ohio) with differing levels of inorganic nutrient inputs. Members of the alpha-, beta-, and gamma-proteobacteria, the Cytophaga–Flavobacteria cluster, and the Domain Bacteria were enumerated using fluorescent in situ hybridization. Detrended canonical correspondence analysis (DCCA) revealed that stoichiometric ratios, especially the dissolved inorganic nitrogen (DIN):soluble reactive phosphorus (SRP) molar ratio (NO₂/NO₃ + NH₄:soluble reactive phosphorus), were correlated with abundance of the various bacterial taxa. However, the patterns were complicated by correlations with single nutrient concentrations and seasonal changes in temperature. Seasonal cycles appeared to play an important role in structuring the community, as there were distinct winter communities and temperature was negatively correlated with abundance of both alpha-proteobacteria and Cytophaga–Flavobacteria. However, nutrients and stoichiometry also appeared to affect the community. Numbers of cells hybridizing the Domain Bacteria probe were correlated with the DOC:DIN ratio, the beta-proteobacteria had a negative correlation with soluble reactive phosphorus concentrations and a positive correlation with the DIN:SRP ratio, and the Cytophaga–Flavobacteria had a significant negative partial correlation with the DIN:SRP ratio. Abundances of the alpha- or gamma-proteobacteria were not directly correlated to nutrient concentrations or stoichiometry. It appears that nutrient stoichiometry may be an important factor structuring bacterial communities; however, it is one of many factors, such as temperature, that are interlinked and must be considered together when studying environmental bacteria.     

Plant growth-promoting activities of fluorescent pseudomonads,isolated from the Iranian soils

Fluorescent pseudomonads are among the most influencing plant growth-promoting rhizobacteria in plants rhizosphere. In this research work the plant growth-promoting activities of 40 different strains of Pseudomonas fluorescens and Pseudomonas putida, previously isolated from the rhizosphere of wheat (Triticum aestivum L.) and canola (Brassica napus L.) and maintained in the microbial collection of Soil and Water Research Institute, Tehran, Iran, were evaluated. The ability of bacteria to produce auxin and siderophores and utilizing P sources with little solubility was determined. Four strains of Wp1 (P. putida), Cfp10 (Pseudomonas sp.), Wp150 (P. putida), and Wp159 (P. putida) were able to grow in the DF medium with ACC. Thirty percent of bacterial isolates from canola rhizosphere and 33% of bacterial isolates from wheat rhizosphere were able to produce HCN. The results indicate that most of the bacteria, tested in the experiment, have plant growth-promoting activities. This is the first time that such PGPR species are isolated from the Iranian soils. With respect to their great biological capacities they can be used for wheat and canola inoculation in different parts of the world, which is of very important agricultural implications.     

Bacterial community dynamics during biostimulation and bioaugmentation experiments aiming at chlorobenzene degradation in groundwater

A set of microcosm experiments was performed to assess different bioremediation strategies, i.e., biostimulation and bioaugmentation, for groundwater contaminated with chlorobenzenes. The biodegradative potential was stimulated either by the supply of electron acceptors (air, (NO ₃ ^– ), to increase the activity of the indigenous bacterial community, or by the addition of aerobic chlorobenzene-degrading bacteria (Pseudomonas putida GJ31, Pseudomonas aeruginosa RHO1, Pseudomonas putida F1CC). Experiments were performed with natural groundwater of the aquifer of Bitterfeld, which had been contaminated with 1,2-dichlorobenzene (1,2-DCB), 1,4-dichlorobenzene (1,4-DCB), and chlorobenzene (CB). The microcosms consisted of airtight glass bottles with 800 mL of natural groundwater and were incubated under in situ temperature (13°C). Behavior of the introduced strains within the indigenous bacterial community was monitored by fluorescent in situ hybridization (FISH) with species-specific oligonucleotides. Dynamics of the indigenous community and the introduced strains within the microcosms were followed by single-strand conformation polymorphism (SSCP) analysis of 16S rDNA amplicons obtained from total DNA of the microbial community. An indigenous biodegradation potential under aerobic as well as anaerobic denitrifying conditions was observed accompanied by fast and specific changes in the natural bacterial community composition. Augmentation with P. aeruginosa RHO1 did not enhance bio-degradation. In contrast, both P. putida GJ31 as well as P. putida F1CC were capable of growing in groundwater, even in the presence of the natural microbial community, and thereby stimulating chlorobenzene depletion. P. putida GJ31 disappeared when the xenobiotics were depleted and P. putida F1CC persisted even in the absence of CB. Detailed statistical analyses revealed that community dynamics of the groundwater microbiota were highly reproducible but specific to the introduced strain, its inoculum size, and the imposed physicochemical conditions. These findings could contribute to the design of better in situ bioremediation strategies for contaminated groundwater.     

Phylogenetic Composition, Spatial Structure, and Dynamics of Lotic Bacterial Biofilms Investigated by Fluorescent in Situ Hybridization and Confocal Laser Scanning Microscopy

Abstract The phylogenetic composition, three-dimensional structure and dynamics of bacterial communities in river biofilms generated in a rotating annular reactor system were studied by fluorescent in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM). Biofilms grew on independently removable polycarbonate slides exposed in the reactor system with natural river water as inoculum and sole nutrient and carbon source. The microbial biofilm community developed from attached single cells and distinct microcolonies via a more confluent structure characterized by various filamentous bacteria to a mature biofilm rich in polymeric material with fewer cells on a per-area basis after 56 days. During the different stages of biofilm development, characteristic microcolonies and cell morphotypes could be identified as typical features of the investigated lotic biofilms. In situ analysis using a comprehensive suite of rRNA-targeted probes visualized individual cells within the alpha-, beta-, and gamma-Proteobacteria as well as the Cytophaga–Flavobacterium group as major parts of the attached community. The relative abundance of these major groups was determined by using digital image analysis to measure specific cell numbers as well as specific cell area after in situ probing. Within the lotic biofilm community, 87% of the whole bacterial cell area and 79% of the total cell counts hybridized with a Bacteria specific probe. During initial biofilm development, beta-Proteobacteria dominated the bacterial population. This was followed by a rapid increase of alpha-Proteobacteria and bacteria affiliated to the Cytophaga–Flavobacterium group. In mature biofilms, alpha-Proteobacteria and Cytophaga–Flavobacteria continued to be the prevalent bacterial groups. Beta-Proteobacteria constituted the morphologically most diverse group within the biofilm communities, and more narrow phylogenetic staining revealed the importance of distinct phylotypes within the beta1-Proteobacteria for the composition of the microbial community. The presence of sulfate-reducing bacteria affiliated to the Desulfovibrionaceae and Desulfobacteriaceae confirmed the range of metabolic potential within the lotic biofilms. Received: 24 September 1998; Accepted: 17 February 1999     

Acquisition of Fe from Various Natural Organic Matter Isolates by Aerobic Pseudomonad Bacteria

Iron (Fe) is an essential nutrient to most microorganisms. Aerobic microorganisms exhibit various strategies for acquiring Fe at near-neutral pH conditions, where Fe oxyhydroxides are insoluble. Although much research has focused on microbial acquisition of Fe from minerals, little is known about Fe acquisition from natural organic matter (NOM). Yet, in surface waters, soils and shallow sediments, Fe is often associated with natural organic matter (NOM), and this NOM-associated Fe could represent an important pool of Fe for microorganisms. Here, we investigated the growth of aerobic Pseudomonas mendocina on soil and surface water NOM samples containing Fe, under Fe-limited conditions. In the presence of NOM, bacteria grew to population sizes greater than in no-Fe-added controls, indicating that the bacteria were able to access Fe associated with NOM. Maximum population size correlated with the NOM-associated Fe concentration. In an additional experiment, Pseudomonas putida was able to acquire Fe from an NOM sample, demonstrating that this ability is not limited to P. mendocina. When Fe was added as 30 μ M FeEDTA plus NOM, together in the same reaction flasks, P. mendocina and P. putida growth was less than in the presence of 30 μM FeEDTA alone. The fact that Fe sources are not simply additive and that the presence of NOM inhibits growth in FeEDTA suggests that further study on the responses of bacteria to a combination of Fe sources is needed to understand the complexities of bacterial Fe acquisition in the subsurface.     

The Effects of Temperature and pH on the Growth of Eight Enteric and Nine Glucose Non-Fermenting Species of Gram-Negative Rods

We studied the heat resistance and the range of growth temperature o gram-negative rods to find one of the bacterial factors governing their infectivity in exogenous and endogenous infections in predisposed patients. Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Pseudomonas aeruginosa, and Acinetobacter calcoaceticus grew equally well at 25, 30, 37, and 42 C. Among other sugar non-fermenting gram-negative rods, six species showed suppressed growth at either or both ends of the incubation temperature range. All the bacterial species tested were killed within 30 min at 60 or 70 C. At 10 C, none of the bacterial strains multiplied, but all survived for 6 hr. Of 17 bacterial species tested, E. coli had the widest range of growth temperature (18–47 C), and also the shortest time necessary for growth to a certain population. Among the sugar non-fermenting rods, A. calcoaceticus had the widest range of growth temperature (20–45 C) and also multiplied rapidly. Pseudomonas strains exhibited slower growth at all temperatures and also had a narrower range of growth temperature than Enterobacteriaceae. Among Pseudomonas species, P. aeruginosa had the widest range of growth temperature (25–42 C) and also showed rapid growth. Pseudomonas cepacia, Achromobacter xylosoxidans, and Alcaligenes faecalis had a narrow range of growth temperature (28–37 C), and Pseudomonas fluorescens, Flavobacterium meningosepticum, and Moraxella grew most rapidly at 30 C. The above results are correlated fairly well with the incidence of clinical cases of infection. The growth attitude of a species of bacteria in response to temperature was considered to be one of the factors affecting the establishment of infection.     

不同分布区胀果甘草原生境土壤微生物群落结构特征及其影响因素

胀果甘草(Glycyrrhiza inflata)主要分布于新疆、甘肃的荒漠区,是耐盐性最强的药用甘草,在改良盐碱地土壤中发挥着重要作用,其原生境土壤微生物群落结构特征是揭示种群分布影响因素及盐碱地修复机制的重要依据。从胀果甘草5个主产区采集原生境土壤,测定土壤理化指标,并采用高通量测序技术,结合Spearman、dbRDA等方法开展微生物群落组成及多样性特征研究,揭示不同分布区的优势微生物群落特征和影响因子。结果表明：真菌群落中曲霉属(Aspergillus)、地丝霉属(Geomyces)、镰刀菌属(Fusarium)和细菌群落中的寡养单胞菌属(Stenotrophomonas)、Marinimicrobium、Idiomarina是野生胀果甘草原生境土壤中的优势微生物类群。不同分布区的土壤真菌多样性和丰富度具有显著差异,但土壤细菌多样性和丰富度差异不显著;部分分布区土壤中的真菌和细菌种类差异较大。土壤理化因子中,土壤含水量和总含盐量对真菌和细菌的群落分布、丰富度有显著影响。原生境含水量与曲霉属(Aspergillus)、镰刀菌属(Fusarium)、链格孢属(Alternaria)...     

Long-term analysis of diesel fuel consumption in a co-culture of Acinetobacter venetianus,Pseudomonas putida and Alcaligenes faecalis

The dynamics of a microbial population isolated from superficial waters of Venice Lagoon and the ability to utilise diesel fuel (n-alkanes mixture C₁₂-C₂₈) as the sole carbon and energy source were studied in a long-term reconstruction experiment. The reconstructed microbial population consisted of three bacterial strains belonging to the species Acinetobacter venetianus, Pseudomonas putida, and Alcaligenes faecalis, which were able to oxidise n-alkanes to alkanoates, n-alkanols to alkanoates, or only n-alkanoates, respectively. Three different approaches: plate counting, cell counting by epifluorescence microscopy with DAPI staining, and by fluorescence in situ hybridisation (FISH) by using a probe conjugate with fluoresceine isothiocyanate specifically targeted towards the 16S rRNA of bacteria belonging to the genus Acinetobacter were used to monitor the growth of the bacterial population. The growth of A. venetianus was stimulated by the presence of other strains, suggesting a beneficial interaction. After the first week of growth A. venetianus cells formed aggregates, as confirmed by confocal microscopy (CLSM), which allowed them to be distinguished from free cells. A relationship between cell number and measured areas (μm²) per aggregate was found. Each cell presented an average surface of 1.21 μm². Each aggregate was formed by a cellular monolayer biofilm consisting of up to several thousands of cells. The A. venetianus aggregates increased in number and size over time, but after two weeks fragmentation events, which had a beneficial effect on the growth of P. putida and A. faecalis, occurred. This revised version was published online in June 2006 with corrections to the Cover Date.     

Identification of Intracellular Bacteria in the Ciliate Balantidium ctenopharyngodoni (Ciliophora,Litostomatea)

The ciliate Balantidium ctenopharyngodoni is the most prominent protist in the guts of grass carp, where it mainly inhabits the creamy luminal contents of the hindgut. Ciliates are generally colonized by microorganisms via phagotrophic feeding. In order to study the intracellular bacteria in this ciliate, we have successfully established it in in vitro culture. Herein, we investigated and compared the bacterial community structures of cultured and freshly collected B. ctenopharyngodoni. The results showed that these two groups exhibited different bacterial communities. The most abundant bacterial family in freshly collected samples was Enterobacteriaceae, while in cultured samples it was Fusobacteriaceae. In addition, a key intracellular bacterium, Cetobacterium somerae, was identified in the cytoplasm of cultured ciliates using fluorescence in situ hybridization (FISH). This study shows that ciliates can retain the intracellular bacteria acquired in the natural habitat for quite a long time, but the bacterial community structure of ciliates eventually changes after a long period of cultivation.     

Verwertung von Trimethylammoniumverbindungen durch Acinetobacter calcoaceticus

Zusammenfassung Die Verwertung von Carnitin und Carnitinderivaten (O-Acylcarnitine, Carnitincarboxyl-derivate) und strukturverwandten Trimethylammoniumverbindungen (Betaine und Stickstoffbasen) durch Acinetobacter calcoaceticus wurde anhand des Wachstums und des quantitativen Nachweises der Metabolite untersucht. Der Stamm wuchs auf l-Carnitin, l-O-Acylcarnitinen und -Butyrobetain als jeweils einziger C-Quelle. Der Verbrauch dieser Verbindungen und das Wachstum korrelierten mit der Spaltung der C-N-Bindung und mit dem gebildeten Trimethylamin. d-Carnitin wurde metabolisiert, wenn als zusätzliche C-Quelle l-Carnitin im Nährmedium vorhanden war, oder wenn die Bakterien mit l-oder dl-Carnitin vorinkubiert worden waren. Mit d-Carnitin als einziger C-Quelle wuchsen die Bakterien jedoch nicht. Die Bakterien oxidierten Cholin zu Glycinbetain in Gegenwart einer zusätzlichen C-Quelle, Glycinbetain selbst wurde nicht assimiliert. In Hinsicht auf den Abbau quaternärer Stickstoffverbindungen besitzt Acinetobacter calcoaceticus im Vergleich zu anderen Carnitin-verwertenden Bakterienarten einen für ihn charakteristischen Stoffwechselweg.

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Utilization of trimethylammonium-compounds by Acinetobacter calcoaceticus

The utilization of carnitine and carnitine derivatives (O-acylcarnitines, carnitine carboxylderivatives) and structure-related trimethylammonium-compounds (betaines and nitrogen-bases) by Acinetobacter calcoaceticus was studied by means of the control of growth and the quantitative detection of metabolites. The strain grew only on l-carnitine, l-O-acylcarnitines, and -butyrobetaine as the sole carbon sources. The utilization of these compounds and the growth correlated with the cleavage of the C-N bond and thereby with the formation of trimethylamine. d-Carnitine was metabolized, if an additional carbon source, like l-carnitine, was present in the incubation mixture, or if the bacteria were preincubated with l-or dl-carnitine, but no growth was observed on d-carnitine as the sole carbon source. The bacteria oxidized choline to glycinebetaine in the presence of additional carbon sources, glycinebetaine itself was not assimilated. With regard to the catabolism of quaternary nitrogen compounds Acinetobacter calcoaceticus shows a different pathway in comparison with other bacterial species metabolizing carnitine.

     

Design, Development, and Use of Molecular Primers and Probes for the Detection of Gluconacetobacter Species in the Pink Sugarcane Mealybug

Molecular tools for the species-specific detection of Gluconacetobacter sacchari, Gluconacetobacter diazotrophicus, and Gluconacetobacter liquefaciens from the pink sugarcane mealybug (PSMB) Saccharicoccus sacchari Cockerell (Homiptera: Pseudococcidae) were developed and used in polymerase chain reactions (PCR) and in fluorescence in situ hybridizations (FISH) to better understand the microbial diversity and the numerical significance of the acetic acid bacteria in the PSMB microenvironment. The presence of these species in the PSMB occurred over a wide range of sites, but not in all sites in sugarcane-growing areas of Queensland, Australia, and was variable over time. Molecular probes for use in FISH were also designed for the three acetic acid bacterial species, and shown to be specific only for the target species. Use of these probes in FISH of “squashed” whole mealybugs indicated that these acetic acid bacteria species represent only a small proportion of the microbial population of the PSMB. Despite the detection of Glac. sacchari, Glac. diazotrophicus, and Glac. liquefaciens by PCR from different mealybugs isolated at various times and from various sugarcane-growing areas in Queensland, Australia, these bacteria do not appear to be significant commensals in the PSMB environment.     

Degradation of furazolidone by bacteria Acinetobacter calcoaceticus T32, Pseudomonas putida SP1 and Proteus mirabilis V7

Furazolidone (FZD) has been widely used as an antibacterial and antiprotozoal feed additive for poultry, cattle and farmed fish. Since FZD has been shown to have mutagenic, genotoxic and potentially carcinogenic properties when tested in a variety of systems, there is an increasing need to find a way to remove FZD from contaminated environments. In this report, three bacterial strains Acinetobacter calcoaceticus T32, Pseudomonas putida SP1 and Proteus mirabilis V7 capable of degrading FZD effectively were isolated, identified and characterized. The reduced FZD concentration after degradation was determined by HPLC. After bacterial cells were grown in the media containing 5 mg l⁻¹ FZD for 5 days, almost all FZD was degraded by A. calcoaceticus T32, and more than 50% of FZD was degraded by P. putida SP1 and P. mirabilis V7, respectively. Bacterial GST activity of A. calcoaceticus T32, P. putida SP1 and P. mirabilis V7 was determined to be influenced by different FZD concentrations. Cytotoxicity analysis showed that FZD was degraded to the metabolites with far less cytotoxicity compared to FZD. The inoculation of bacterial strains A. calcoaceticus T32, P. putida SP1 and P. mirabilis V7 into FZD-contained media resulted in a higher degradation efficiency than natural degradation, which indicated the potential application of these strains in treatment of FZD-polluted freshwater or seawater environments.