Enrichment of subgingival microflora on human serum leading to accumulation of Bacteroides species, Peptostreptococci and Fusobacteria

This study was undertaken to identify ecological factors that favour opportunistic pathogenic species in the subgingival microflora. In a first approach, human serum as a substitute for gingival exudate, was used for batch-wise enrichment of subgingival plaque. The microflora resulting after 5-6 enrichment steps consisted of black-pigmented and non-black-pigmented Bacteroides species, Peptostreptococcus micros and Fusobacterium nucleatum as the main organisms. It is noted that the same group of species was found to be enriched independent upon the origin of the subgingival plaque sample. It was suggested that these organisms are favoured by the increased flow of gingival exudate during inflammation. The consortium of organisms was capable of selective degradation of serum (glyco-)proteins. Four different types of degradation occurred. After a prolonged period of growth complete degradation of immunoglobulins, haptoglobin, transferrin and complement C3c was observed. Partial degradation of immunoglobulins, haptoglobin, transferrin, albumin, alpha 1-antitrypsin and complement C3c and C4 was generally observed after 48 h of growth. Besides, immunoglobulin protease activity yielding Fc and Fab fragments was found. The consortium was also capable of consuming carbohydrate side-chains as indicated by an altered electrophoretic mobility of the serum glycoproteins.     

Biodegradation of p-nitrophenol by microalgae

A study was made on the use of a mixed microalgal consortium to degrade p-nitrophenol. The consortium was obtained from a microbial community in a waste container fed with the remains and by-products of medium culture containing substituted aromatic pollutants (nitrophenols, chlorophenols, fluorobenzene). After selective enrichment with p-nitrophenol (p-NP), followed by an antibiotic treatment, an axenic microalgal consortium was recovered, which was able to degrade p-nitrophenol. At a concentration of 50 mg L^–1, total degradation occurred within 5 days. Two species, Chlorella vulgaris var. vulgaris f. minuscula and Coenochloris pyrenoidosa, were isolated from the microalgal consortium. The species were able to accomplish p-NP biodegradation when cultured separately, although Coenochloris pyrenoidosa was more efficient, achieving the same degradation rate as the original axenic microalgal consortium. When Coenochloris pyrenoidosa was associated with Chlorella vulgaris in a 3:1 ratio, complete removal of the nitro-aromatic compound occurred within three days. This is apparently the first report on the degradation of a nitro-aromatic compound by microalgae.     

Anaerobic degradation of p-xylene in sediment-free sulfate-reducing enrichment culture

Anaerobic degradation of p-xylene was studied with sulfate-reducing enrichment culture. The enrichment culture was established with sediment-free sulfate-reducing consortium on crude oil. The crude oil-degrading consortium prepared with marine sediment revealed that toluene, and xylenes among the fraction of alkylbenzene in the crude oil were consumed during the incubation. The PCR-denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene for the p-xylene degrading sulfate-reducing enrichment culture showed the presence of the single dominant DGGE band pXy-K-13 coupled with p-xylene consumption and sulfide production. Sequence analysis of the DGGE band revealed a close relationship between DGGE band pXy-K-13 and the previously described marine sulfate-reducing strain oXyS1 (similarity value, 99%), which grow anaerobically with o-xylene. These results suggest that microorganism corresponding to pXy-K-13 is an important sulfate-reducing bacterium to degrade p-xylene in the enrichment culture.     

Microbiological degradation of the herbicide dicamba

Summary Pseudomonas paucimobilis was isolated from a consortium which was capable of degrading dicamba (3,6-dichloro-2-methoxybenzoic acid) as the sole source of carbon. The degradation of dicamba byP. paucimobilis and the consortium was examined over a range of substrate concentration, temperature, and pH. In the concentration range of 100–2000 mg dicamba L^–1 (0.5–9.0 mM), the degradation was accompanied by a stoichiometric release of 2 mol of Cl^– per mol of dicamba degraded. The cultures had an optimum pH 6.5–7.0 for dicamba degradation. Growth studies at 10°C, 20°C, and 30°C yielded activation energy values in the range of 19–36 kcal mol^–1 and an average Q₁₀ value of 4.0. Compared with the pure cultureP. paucimobilis, the consortium was more active at the lower temperature.     

Degradation of polychlorinated biphenyl (PCB) by a consortium obtained from a contaminated soil composed of Brevibacterium,Pandoraea and Ochrobactrum

An indigenous polychlorinated biphenyl (PCB)-degrading bacterial consortium was obtained from soils contaminated by transformer oil with a high content of PCBs. The PCB degrader strains were isolated and identified as Brevibacterium antarcticum, Pandoraea pnomenusa, and Ochrobactrum intermedium by 16S rRNA gene sequence phylogenetic analysis. The PCB-degrading ability of the consortium and of individual strains was determined by using GC/MS. The PCB-degrading capacities of the consortium were evaluated for three concentrations of transfomer oil ranging from 55 to 152 μM supplemented with 0.001% biphenyl and 0.1% of Tween 80 surfactant. PCB biodegradation by the consortium was favored in the presence of both additives and the greatest extent of biodegradation (67.5%) was obtained at a PCB concentration of 55 μM. Each bacterial species exhibited a particular pattern of degradation relating to specific PCB congeners. Isolated strains showed a moderate degradation capability towards tetra-, hepta-, and octa-chlorobiphenyls; although no effect on penta-, hexa-, and nona-chlorobiphenyls was observed. Recently, PCB degradation capacity was recognized in a Pandorea member; however, this is the first study that describes the ability of Brevibacterium and Ochrobactrum species to degrade PCBs.     

Growth stimulation of Treponema denticola by periodontal microorganisms

Previous experiments have indicated that enrichment of subgingival plaque in human serum can lead to the accumulation of Treponema denticola. T. denticola depends on bacterial interactions for its growth in serum. Aim of the present study was to identify specific microorganisms involved in the growth stimulation of T. denticola. To this end, strains isolated from previous plaque enrichment cultures were tested for growth stimulation in co-cultures with T. denticola. In addition, growth of T. denticola was tested in culture filtrates of the same strains, Bacteroides intermedius, Eubacterium nodatum, Veillonella parvula and Fusobacterium nucleatum were found to enhance growth of T. denticola in co-cultures. A continuous co-culture of T. denticola, F. nucleatum and B. intermedius in human serum gave very high levels of T. denticola, up to 3.10(9).ml-1. Mechanisms involved in growth stimulation may include the ability of B. intermedius and E. nodatum to cleave the protein-core of serum (glyco-)proteins, making these molecules accessible for degradation by T. denticola. In addition, E. nodatum was found to produce a low-molecular weight growth-factor for T. denticola, that was heat-stable and acid as well as alkaline resistant. V. parvula may provide peptidase activities complementary to those of T. denticola. The nature of the growth enhancing activity of F. nucleatum is yet unknown. The data support the dependency of T. denticola on other bacterial species for growth in the periodontal pocket.     

Degradation of benzene compounds by yeasts in acidic soils

Attemps were made to demonstrate the role of yeasts in the degradation of benzene compounds under natural soil conditions. Yeasts were isolated from acidic sandy soil supplied with benzene compounds. For this purpose the slant culture method was used. Growth on the benzene compounds took place on solid growth media at 10°C. Several yeast species were isolated: Leucosporidium scottii, Rhodotorula aurantiaca, Rhodotorula mucilaginosa, Trichosporon dulcitum, Trichosporon moniliiforme and Schizoblastosporion starkeyi-henricii. Cryptococcus humicolus and Cryptococcus laurentii were isolated from liquid enrichment cultures. All these strains assimilated several benzene compounds in pure culture.Cresol removal from contaminated soil was speeded up by inoculation with Rhodotorula aurantiaca G36. It was demonstrated that this yeast utilized this compound in competition with the soil microflora.     

Biodegradation of disperse dye brown 3REL by microbial consortium of Galactomyces geotrichum MTCC 1360 and Bacillus sp. VUS

The consortium-GB (Galactomyces geotrichum MTCC 1360 and Bacillus sp. VUS) exhibited 100% decolorization ability with the dye Brown 3REL within 2 h at shaking condition with optima of pH 7 and at 50°C. However, G. geotrichum MTCC 1360 showed 39% decolorization within 24 h and Bacillus sp. VUS took 5 h for 100% decolorization, when incubated individually. Additional carbon and nitrogen sources like, starch, peptone, and urea were found to enhance decolorization. Induction in lignin peroxidase, tyrosinase, and riboflavin reductase was observed in consortium as that of individual organisms. GCMS identification showed different metabolites formed using consortium (2-(6,8-dichloro-quinazolin-4yloxy)-acetyl-urea and 2-(6,8-dichloro-quinazolin-4yloxy)-acetyl-formamide) and Bacillus sp. VUS (6,8-dichloro-4 methoxy-quinazoline) after 2 h of incubation with Brown 3REL. G. geotrichum MTCC 1360 showed minor modifications in structure of Brown 3REL. Phytotoxicity revealed non toxic nature of metabolites. This consortium-GB was also able to decolorize various industrial dyes.     

降解尿酸乳酸菌复合菌系的筛选与菌株组合提升降解效果

【背景】高尿酸症由血液中尿酸含量明显升高而导致,利用乳酸菌对人体的益生作用缓解高尿酸血症越来越受到关注。【目的】获得具有降解尿酸能力的乳酸菌复合菌系与纯培养菌株。【方法】以泡菜为样品来源,以尿酸为底物,采用MRS培养基筛选降解尿酸的乳酸菌复合菌系,通过高效液相色谱法测定复合菌系对尿酸的降解能力。【结果】得到一组乳酸菌复合菌系,当培养温度为37 °C、pH值为6.20、静置培养72 h后复合菌系对尿酸的降解率为12.08%;通过优化培养条件,当该菌系在以牛肉膏为单一氮源、初始pH值为5.00、温度为35 °C的条件下培养72 h,尿酸降解率上升至17.19%,降解率比优化前提高了42.3%;从该菌系中分离出两株具有尿酸降解能力的菌株UA-1与UA-2,它们的尿酸降解率分别为10.85%和8.65%;通过形态学观察和16S rRNA基因序列分析,经鉴定两株菌均为布氏乳杆菌(Lactobacillus buchneri)。将两株单菌组合降解尿酸试验发现,UA-1与UA-2比例为2:1的尿酸降解率为20.2%,比原复合菌系的降解能力提高了67.22%。【结论】研究证明了乳酸菌复合菌系对尿酸的降解能力优于单个菌株,为后续利用乳酸菌复合菌系应用提供了数据支持。     

Degradation and corrosive activities of fungi in a diesel–mild steel–aqueous system

The fungi Aspergillus fumigatus, Hormoconis resinae and Candida silvicola were isolated from the fuel/water interfacial biomass in diesel storage tanks in Brazil. Their corrosive activities on mild steel ASTM A 283-93-C, used in storage tanks for urban diesel, were evaluated after various times of incubation at 30 °C in a modified Bushnell–Haas mineral medium (without chlorides) with diesel oil as sole source of carbon. Their ability to degrade diesel oil was evaluated after growth for 30 and 60 days. The fungus Aspergillus fumigatus and the consortium of all three organisms showed the highest production of biomass; A. fumigatus gave the greatest value for steel weight loss and produced the greatest reduction in pH of the aqueous phase. Solid phase microextraction (SPME) showed that the main acid present in the aqueous phase after 60 days incubation with A. fumigatus was propionic acid. Polarization curves indicated that microbial activity influenced the anodic process, probably by the production of corrosive metabolites, and that this was particularly important in the case of A. fumigatus. This fungus preferentially degraded aliphatic hydrocarbons of chain lengths C₁₁--C₁₃ in the diesel, producing 47.7, 37.5 and 51% reductions in C₁₁, C₁₂ and C₁₃, respectively. It produced more degradation than the consortium after 60 days incubation. It is likely that the presence of other species in the consortium inhibited the growth of A. fumigatus, thus resulting in a lower rate of diesel fuel degradation.     

Regulation of amino acid and glucose dissimilation in so-called ammonifiers and in other soil microorganisms

Pseudomonas acidovorans and P. putida, isolated from an enrichment culture with casein hydrolysate, and Agrobacterium radiobacter and Torulopsis sp., isolated from a glucose enrichment, were compared with respect to the physiology of ammonification. Decreasing ammonifying ability as well as increasing repression of the synthesis of amino acid degrading enzymes by glucose were found in the above order of organisms. In degradation sequences, observed with P. putida and A. radiobacter as test organisms, substances dissimilated prior to others had both, enhancing and repressing effects on the oxidation of the other compounds. This fact was parallelled by the observation, that in these two bacteria, glucose and single amino acids, when added to the same medium, exerted mutual repression of the synthesis of catabolic enzymes of their partners. The ecological significance of this type of regulation has been discussed.     

Combined metabolic activity within an atrazine-mineralizing community enriched from agrochemical factory soil

The main objective of this work was to characterize an atrazine-mineralizing community originating from agrochemical factory soil, especially to elucidate the catabolic pathway and individual metabolic and genetic potentials of culturable members. A stable four-member bacterial community, characterized by colony morphology and 16S rDNA sequencing, was rapidly able to mineralize atrazine to CO₂ and NH₃. Two primary organisms were identified as Arthrobacter species (ATZ1 and ATZ2) and two secondary organisms (CA1 and CA2) belonged to the genera Ochrobactrum and Pseudomonas, respectively. PCR assessment of atrazine-degrading genetic potential of the community, revealed the presence of trzN, trzD, atzB and atzC genes. Isolates ATZ1 and ATZ2 were capable of dechlorinating atrazine to hydroxyatrazine and contained the trzN gene. ATZ2 further degraded hydroxyatrazine to cyanuric acid and contained atzB and atzC genes whereas ATZ1 contained atzC but not atzB. Isolates CA1 and CA2 grew on cyanuric acid and contained the trzD gene. Complete atrazine degradation was a result of the combined metabolic attack on the atrazine molecule, and complex interactions may exist between the community members sharing carbon and nitrogen from atrazine mineralization.Scientific relevance: Despite numerous reports on atrazine degradation by pure bacterial cultures, the pathways and the atrazine-degrading gene combinations harboured by bacterial communities are only poorly described. In this work, we characterized a four-member atrazine-mineralizing community enriched from an agrochemical factory soil, which was capable of rapidly metabolizing atrazine to CO₂. This study will contribute towards better understanding of the genetic potential and metabolic activities of atrazine-degrading communities, which are generally considered to be responsible for atrazine mineralization in the natural environment.     

Decolourization and Detoxification of Methyl Red by Aerobic Bacteria from A Wastewater Treatment Plant

Bacterial cultures from a wastewater treatment plant degraded a toxic azo dye (methyl red) by decolourization. Complete decolourization using a mixed-culture was achieved at pH 6, 30 °C within 6 h at 5 mg/l methyl red concentration, and 16 h at 20—30 mg/l. Four bacterial species were isolated that were capable of growth on methyl red as the sole carbon source, and two were identified, namely Vibrio logei and Pseudomonas nitroreducens. The Vibrio species showed the highest methyl red degradation activity at the optimum conditions of pH 6--7, and 30—35 °C. Analysis by NMR showed that previously reported degradation products 2-aminobenzoic acid and N,N-dimethyl-1,4-phenylenediamine were not observed. The decolourized dye was not toxic to a monkey kidney cell line (COS-7) at a concentration of 250 μM. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of biodelignification of rice straw on humification and humus quality by Phanerochaete chrysosporium and Streptomyces badius

The effect of biodelignification of rice straw by two different ligninolytic organisms, Phanerochaete chrysosporium (white-rot fungus) and Streptomyces badius (actinomycetes), on humus quality was investigated during a 56-day incubation at 30 °C. Lignin degradation, the release of humic extract (HE), humic acid (HA) and fulvic acid (FA), E4/E6 ratio of HA, and humification index (HI, HA/FA) were measured during the incubation. Lignin was degraded by both organisms, but to different extents. Lignin was degraded to 41% and 31% by P. chrysosporium and S. badius, respectively. HE released by P. chrysosporium and S. badius were, respectively, 2.10 and 2.13 times larger than that in the control at the maximum values. A significant correlation between lignin degradation and humus-related parameters involving HA fraction showed that both organisms are converting lignin to humic substances.     

Denitrification in a binary culture and thiocyanate metabolism in Thiohalophilus thiocyanoxidans gen. nov. sp. nov. – a moderately halophilic chemolithoautotrophic sulfur-oxidizing Gammaproteobacterium from hypersaline lakes

Anaerobic enrichment culture with thiocyanate as electron donor and nitrate as electron acceptor at 2 M NaCl inoculated with a mixture of sediments from hypersaline lakes in Kulunda Steppe (Altai, Russia) resulted in a selection of a binary consortium of moderately halophilic, obligately chemolithoautotrophic sulfur-oxidizing bacteria (SOB) capable of complete denitrification of nitrate with thiosulfate as the electron donor. One consortium member, strain HRhD 3sp, was isolated into pure culture with nitrate and thiosulfate using a density gradient. This strain was responsible for the reduction of nitrate to nitrite in the consortium, while a second strain, HRhD 2, isolated under microoxic conditions with thiosulfate as substrate, was capable of anaerobic growth with nitrite and thiosulfate. Nitrite, either as substrate or as product, was already toxic at very low concentrations for both strains. As a result, optimal growth under anaerobic conditions could only be achieved within the consortium. On the basis of phylogenetic analysis, both organisms were identified as new lineages within the Gammaproteobacteria. As well as thiosulfate, strain HRhD 2 can also use thiocyanate as electron donor, representing a first halophilic SOB capable of growth with thiocyanate at 2–4 M NaCl. Product and enzymatic analysis identified the “carbonyl sulfide (COS) pathway” of primary thiocyanate degradation in this new species. On the basis of phenotypic and genetic analysis, strain HRhD 2 is proposed to be assigned to a new genus and species Thiohalophilus thiocyanoxidans. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Biodegradation of 2-Nitrotoluene by <Emphasis Type="Italic">Micrococcus</Emphasis> sp. strain SMN-1

A bacterial consortium capable of degrading nitroaromatic compounds was isolated from pesticide-contaminated soil samples by selective enrichment on 2-nitrotoluene as a sole source of carbon and energy. The three different bacterial isolates obtained from bacterial consortium were identified as Bacillus sp. (A and C), Bacillus flexus (B) and Micrococcus sp. (D) on the basis of their morphological and biochemical characteristics and by phylogenetic analysis based on 16S rRNA gene sequences. The pathway for the degradation of 2-nitrotoluene by Micrococcus sp. strain SMN-1 was elucidated by the isolation and identification of metabolites, growth and enzymatic studies. The organism degraded 2-nitrotoluene through 3-methylcatechol by a meta-cleavage pathway, with release of nitrite.     

Biodegradation of 1,4-dioxane by a <Emphasis Type="Italic">Flavobacterium</Emphasis>

A dioxane-degrading consortium was enriched from soil obtained from a contaminated groundwater plume. The enriched consortium did not use dioxane as the sole source of carbon and energy but co-metabolized dioxane in the presence of tetrahydrofuran (THF). THF and dioxane concentrations up to 1000 ppm were degraded by the enriched consortium in about 2 weeks with a longer lag phase observable at 1000 ppm. Three colonies from the enriched consortium were then obtained on agar plates containing basal salts and glucose as the carbon source. Only one of the three colonies was capable of dioxane degradation. Further enrichment of this colony in liquid media led to a pure culture that grew on glucose and co-metabolically degraded dioxane after THF degradation. The rate and extent of dioxane degradation of this isolate increased with increasing THF concentration. This isolate was subsequently identified as a Flavobacterium by 16S rDNA sequencing. Using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analysis of microbial populations, Flavobacterium was determined to be the dominant species in the enriched consortium and was distinct from the two other colonies that did not degrade dioxane. This is the first report of a dioxane-degrading Flavobacterium which is phylogenetically distinct from any previously identified dioxane degrader.     

Utilization of aminoaromatic acids by a methanogenic enrichment culture and by a novel<Emphasis Type="Italic"> Citrobacter freundii</Emphasis> strain

Following incubation of mesophilic methanogenic floccular sludge from a lab-scale upflow anaerobic sludge bed reactor used to treat cattle manure wastewater, a stable 5-aminosalicylate-degrading enrichment culture was obtained. Subsequently, a Citrobacter freundii strain, WA1, was isolated from the 5-aminosalicylate-degrading methanogenic consortium. The methanogenic enrichment culture degraded 5-aminosalicylate completely to CH₄, CO₂ and NH₄ ⁺, while C. freundii strain WA1 reduced 5-aminosalicylate with simultaneous deamination to 2-hydroxybenzyl alcohol during anaerobic growth with electron donors such as pyruvate, glucose or serine. When grown on pyruvate, C. freundii WA1 converted 3-aminobenzoate to benzyl alcohol and also reduced benzaldehyde to benzyl alcohol. Pyruvate was fermented to acetate, CO₂, H₂ and small amounts of lactate, succinate and formate. Less lactate (30%) was produced from pyruvate when C. freundii WA1 grew with 5-aminosalicylate as co-substrate.     

Utilization of homoserine lactone as a sole source of carbon and energy by soil Arthrobacter and Burkholderia species

Homoserine lactone (HSL) is a ubiquitous product of metabolism. It is generated by all known biota during the editing of certain mischarged aminoacyl-tRNA reactions, and is also released as a product of quorum signal degradation by bacterial species expressing acyl-HSL acylases. Little is known about its environmental fate over long or short periods of time. The mammalian enzyme paraoxonase, which has no known homologs in bacteria, has been reported to degrade HSL via a lactonase mechanism. Certain strains of Variovorax and Arthrobacter utilize HSL as a sole source of nitrogen, but not as a sole source of carbon or energy. In this study, the enrichment and isolation of four strains of soil bacteria capable of utilizing HSL as a carbon and energy source are described. Phylogenetic analysis of these isolates indicates that three are distinct members of the genus Arthrobacter, whereas the fourth clusters within the non-clinical Burkholderia. The optimal pH for growth of the isolates ranged from 6.0 to 6.5, at which their HSL-dependent doubling times ranged from 1.4 to 4 h. The biodegradation of HSL by these 4 isolates far outpaced its chemical decay. HSL degradation by soil bacteria has implications for the consortial mineralization of acyl-homoserine lactones by bacteria associated with quorum sensing populations.     

Optimized cultivation of highly-efficient degradation bacterial strains and their degradation ability towards pyrene

Two bacterial strains, Py1 and Py4, have been tamed and isolated through long cultivation with polycyclic aromatic hydrocarbon—pyrene as the single carbon source. It has been proven that they are both highly-efficient pyrene degrading bacteria and both Bacillus sp.. The pyrene degradation ability of separated Py1, Py4 and the consortium of equal Py1 and Py4 was studied in this project. It is shown that pyrene degradation rates were 88% in 10hr by Py1, 84% in 14hr by Py4, and 88% in 8hr by the consortium. It was also determined that the best degradation temperatures were 37°C and pH 7.0 respectively. The influence of different nutrient substrates added in the degradation experiments was also studied. It was shown that sodium salicylate, sodium acetate and yeast extract had obvious simulative effect, but glucose had no obvious effect. __________ Translated from Acta Scientiarum Naturalium Universitatis Nankaiensis (Natural Science Edition) 2006, 39: 71–74 [译自: 南开大学学报 (自然科学版)]