Degradation of Lignin Compounds by Bacteria from Termite Guts

By incubating bacteria from the gut of the termite, Nasutitermes takasagoensis, in a culture medium containing a ligninic compound, direct evidence that lignin-biodegradation occurs in the gut of termites was obtained. The bacteria were capable of degrading ligninic compounds. 28% of dealkalized lignin was degraded and lignin dimer compounds, which have a linkage proper to lignin, such as -O-4, -1, phenylcoumarane and biphenyl bonds, were degraded by 60 % to 95 %.     

Efficient Hydrogen-Dependent Carbon Dioxide Reduction by Escherichia coli

1. Download high-res image (119KB)
2. Download full-size image

     

九孔鲍消化道及养殖水体中异养细菌胞外产物的分析

从汕尾健生鲍鱼场养殖水体及鲍鱼消化道中分离筛选到26株异养细菌,分析了其胞外产物,并采用API条带对其进行了种类鉴定。结果表明,就整体而言,成鲍消化道菌株产蛋白酶、淀粉酶、明胶酶和溶血能力均高于养殖水体的菌株,而产脂肪酶和卵磷脂酶菌株的比例则低于后者。无论是消化道还是养殖水体,均存在着分泌胞外产物能力极强的菌株,且大部分为鞘氨醇单胞菌。因此,在该养殖环境中,鞘氨醇单胞菌应视为一种主要的条件致病菌,同时消化道和养殖水体均应视为潜在致病菌的源泉。此外,在考虑细菌对水产经济动物的致病作用时,除了优势种类外,还应从菌群结构的角度出发,考虑整个细菌群落胞外产物的作用。     

The Termite Gut Microflora as an Oxygen Sink: Microelectrode Determination of Oxygen and pH Gradients in Guts of Lower and Higher Termites

Clark-type oxygen microelectrodes and glass pH microelectrodes, each with a tip diameter of <=10 (mu)m, were used to obtain high-resolution profiles of oxygen concentrations and pH values in isolated termite guts. Radial oxygen profiles showed that oxygen penetrated into the peripheral hindgut contents up to about 150 to 200 (mu)m below the epithelial surface in both the lower termite Reticulitermes flavipes (Kollar) and the higher termite Nasutitermes lujae (Wasmann). Only the central portions (comprising less than 40% of the total volume) of the microbe-packed, enlarged hindgut compartments ("paunches") were completely anoxic, indicating that some members of the hindgut microbiota constitute a significant oxygen sink. From the slopes of the oxygen gradients, we estimated that the entire paunches (gut tissue plus resident microbiota) of R. flavipes and N. lujae accounted for 21 and 13%, respectively, of the respiratory activity of the intact animals. Axial oxygen profiles also confirmed that in general, only the paunches were anoxic in their centers, whereas midguts and posterior hindgut regions contained significant amounts of oxygen (up to about 50 and 30% air saturation, respectively). A remarkable exception to this was the posterior portion of an anterior segment (the P1 segment) of the hindgut of N. lujae, which was completely anoxic despite its small diameter ((apprx=)250 (mu)m). Axial pH profiles of the guts of Nasutitermes nigriceps (Haldeman) and Microcerotermes parvus (Haviland) revealed that there were extreme shifts as we moved posteriorly from the midgut proper (pH (apprx=)7) to the P1 segment of the hindgut (pH >10) and then to the P3 segment (paunch; pH (apprx=)7). The latter transition occurred at the short enteric valve (P2 segment) and within a distance of less than 500 (mu)m. In contrast, R. flavipes, which lacks a readily distinguishable P1 segment, did not possess a markedly alkaline region, and the pH around the midgut-hindgut junction was circumneutral. The oxic status of the peripheral hindgut lumen and its substantial oxygen consumption, together with previous reports of large numbers of aerobic and facultatively anaerobic bacteria in the hindgut microflora, challenge the notion that termite hindguts are a purely anoxic environment and, together with the steep axial pH gradients in higher termites, refine our concept of this tiny microbial habitat.     

Stenoxybacter acetivorans gen. nov., sp. nov., an Acetate-Oxidizing Obligate Microaerophile among Diverse O2-Consuming Bacteria from Termite Guts

In termite hindguts, fermentative production of acetate—a major carbon and energy source for the insect—depends on efficient removal of inwardly diffusing oxygen by microbes residing on and near the hindgut wall. However, little is known about the identity of these organisms or about the substrate(s) used to support their respiratory activity. A cultivation-based approach was used to isolate O₂-consuming organisms from hindguts of Reticulitermes flavipes. A consistently greater (albeit not statistically significant) number of colonies developed under hypoxia (2% [vol/vol] O₂) than under air, and the increase coincided with the appearance of morphologically distinct colonies of a novel, rod-shaped, obligately microaerophilic β-proteobacterium that was <95% similar (based on the 16S rRNA gene sequence) to its closest known relative (Eikenella corrodens). Nearly identical organisms (and/or their 16S rRNA genes) were obtained from geographically separated and genetically distinct populations of Reticulitermes. PCR-based procedures implied that the novel isolates were autochthonous to the hindgut of R. flavipes and comprised ca. 2 to 7% of the hindgut prokaryote community. Representative strain TAM-DN1 utilized acetate and a limited range of other organic and amino acids as energy sources and possessed catalase and superoxide dismutase. On solid medium, the optimal O₂ concentration for growth was about 2%, and no growth occurred with O₂ concentrations above 4% or under anoxia. However, cells in liquid medium could grow with higher O₂ concentrations (up to 16%), but only after proportionately extended lag phases. The genetic and physiological distinctiveness of TAM-DN1 and related strains supports their recognition as a new genus and species, for which the name Stenoxybacter acetivorans gen. nov., sp. nov. is proposed.     

Toxicity of Hexavalent Chromium and Its Reduction by Bacteria Isolated from Soil Contaminated with Tannery Waste

An Arthrobacter sp. and a Bacillus sp., isolated from a long-term tannery waste contaminated soil, were examined for their tolerance to hexavalent chromium [Cr(VI)] and their ability to reduce Cr(VI) to Cr(III), a detoxification process in cell suspensions and cell extracts. Both bacteria tolerated Cr(VI) at 100 mg/ml on a minimal salts agar medium supplemented with 0.5% glucose, but only Arthrobacter could grow in liquid medium at this concentration. Arthrobacter sp. could reduce Cr(VI) up to 50 μg/ml, while Bacillus sp. was not able to reduce Cr(VI) beyond 20 μg/ml. Arthrobacter sp. was distinctly superior to the Bacillus sp. in terms of their Cr(VI)-reducing ability and resistance to Cr(VI). Assays with permeabilized (treated with toluene or Triton X 100) cells and crude extracts demonstrated that the Cr(VI) reduction was mainly associated with the soluble protein fraction of the cell. Arthrobacter sp. has a great potential for bioremediation of Cr(VI)-containing waste. Received: 13 June 2002 / Accepted: 13 September 2002     

Microbiological Oxidation of Antimony(III) with Oxygen or Nitrate by Bacteria Isolated from Contaminated Mine Sediments

Bacterial oxidation of arsenite [As(III)] is a well-studied and important biogeochemical pathway that directly influences the mobility and toxicity of arsenic in the environment. In contrast, little is known about microbiological oxidation of the chemically similar anion antimonite [Sb(III)]. In this study, two bacterial strains, designated IDSBO-1 and IDSBO-4, which grow on tartrate compounds and oxidize Sb(III) using either oxygen or nitrate, respectively, as a terminal electron acceptor, were isolated from contaminated mine sediments. Both isolates belonged to the Comamonadaceae family and were 99% similar to previously described species. We identify these novel strains as Hydrogenophaga taeniospiralis strain IDSBO-1 and Variovorax paradoxus strain IDSBO-4. Both strains possess a gene with homology to the aioA gene, which encodes an As(III)-oxidase, and both oxidize As(III) aerobically, but only IDSBO-4 oxidized Sb(III) in the presence of air, while strain IDSBO-1 could achieve this via nitrate respiration. Our results suggest that expression of aioA is not induced by Sb(III) but may be involved in Sb(III) oxidation along with an Sb(III)-specific pathway. Phylogenetic analysis of proteins encoded by the aioA genes revealed a close sequence similarity (90%) among the two isolates and other known As(III)-oxidizing bacteria, particularly Acidovorax sp. strain NO1. Both isolates were capable of chemolithoautotrophic growth using As(III) as a primary electron donor, and strain IDSBO-4 exhibited incorporation of radiolabeled [¹⁴C]bicarbonate while oxidizing Sb(III) from Sb(III)-tartrate, suggesting possible Sb(III)-dependent autotrophy. Enrichment cultures produced the Sb(V) oxide mineral mopungite and lesser amounts of Sb(III)-bearing senarmontite as precipitates.     

Degradation of Parathion by Bacteria Isolated from Flooded Soil

Two bacteria, Bacillus sp. and Pseudomonas sp., were isolated from parathionamended flooded alluvial soil which exhibited parathion-hydrolyzing ability. Bacillus sp. readily liberated nitrite from the hydrolysis product, p-nitrophenol, but not from intact parathion. Pseudomonas sp. hydrolyzed parathion and then released nitrite from p-nitrophenol. These studies establish bacterial degradation of parathion past the p-nitrophenol stage to the end product, nitrite.     

Degradation of Methylmercury by Bacteria Isolated from Environmental Samples

A total of 207 bacterial cultures, isolated from environmental samples, was screened for ability to degrade methylmercury. Of these, 30 were found positive for aerobic demethylation. Twenty-two of these were shown to be facultative anaerobes and 21 of these degraded methylmercury anaerobically. All positive species volatilized methylmercury aerobically, and methane was produced as a degradation product. Although methylmercury degradation was complete in most cases, material balances indicated some of the inorganic mercury formed was not volatilized and is presumed bound to the cells. All positive isolates were tolerant to at least 0.5 mug of methylmercury per ml, and the extent of volatilization of mercury increased with concentration to the threshold value. The results indicate that demethylating species are prevalent in the environment and may be important in suppressing the methylmercury content of sediments.     

九孔鲍养殖水体及其肠道不同菌群抗药性研究*

为更好地防治鲍鱼病害的发生和流行,对分离自广东汕尾健生鲍鱼养殖场九孔鲍养殖环境及其肠道中不同细菌菌群的耐药性进行了研究。结果表明,四环素、青霉素G、卡那霉素、丁胺卡那霉素和新生霉素均对绝大多数异养菌和弧菌菌株都不敏感或无作用;相反,氟哌酸、红霉素、氯霉素以及环丙沙星等则均对它们比较敏感;复方新诺明、链霉素和多粘霉素B对弧菌菌株均有作用,而且多粘霉素B也对水体中的异养菌群相当有效。     

Utilization of Ammonia Nitrogen by Intestinal Bacteria Isolated from Pigs

In a medium containing ammonia, proteose peptone, and cysteine as nitrogen sources, 17 of 24 Bacteroidaceae strains, 3 of Selenomonas strains, 1 of 7 curved rods, 3 of 7 Spirochaetaceae strains, 8 of 20 Eubacterium strains, 8 of 13 Peptococcaceae strains, 3 of 4 Clostridium strains, 19 of 20 Enterobacteriaceae strains, and 1 of 8 Streptococcus strains utilized ammonia nitrogen preferentially to proteose peptone nitrogen. To determine the ability of intestinal microbes to synthesize amino acids from ammonia, ammonia utilization by Bacteroides ruminicola strain 9 was studied in defined media containing ammonia and other nitrogen sources. In another medium containing ammonia, proteose peptone, and cysteine as nitrogen sources, ammonia was preferentially utilized even when the proteose peptone nitrogen content was eight times greater than that of ammonia nitrogen. In a medium containing ammonia, an amino acid, and cysteine, the lowest uptake of ammonia nitrogen was observed when the medium contained aspartic acid, glutamic acid, threonine, or alanine; but ammonia was utilized more effectively than any of the amino acids. Incorporation of ¹⁵N from [¹⁵N]ammonia into bacterial amino acids was studied. ¹⁵N was incorporated into every amino acid of B. ruminicola strain 9, and the highest uptake was observed in aspartic acid and alanine.     

Conversion of Unsaturated Fatty Acids by Bacteria Isolated from Compost

A compost mixture amended with soybean oil was enriched in microorganisms that transformed unsaturated fatty acids (UFAs). When oleic acid or 10-ketostearic acid was the selective fatty acid, Sphingobacterium thalpophilum (NRRL B-23206, NRRL B-23208, NRRL B-23209, NRRL B-23210, NRRL B-23211, NRRL B-23212), Acinetobacter spp. (NRRL B-23207, NRRL B-23213), and Enterobacter cloacae (NRRL B-23264, NRRL B-23265, NRRL B-23266) represented isolates that produced either hydroxystearic acid, ketostearic acid, or incomplete decarboxylations. When ricinoleic (12-hydroxy-9-octadecenoic) acid was the selective UFA, Enterobacter cloacae (NRRL B-23257, NRRL B-23267) and Escherichia sp. (NRRL B-23259) produced 12-C and 14-C homologous compounds, and Pseudomonas aeruginosa (NRRL B-23256, NRRL B-23260) converted ricinoleate to a trihydroxyoctadecenoate product. Also, various Enterobacter, Pseudomonas, and Serratia spp. appeared to decarboxylate linoleate substrate incompletely. These saprophytic, compost bacteria were aerobic or facultative anaerobic Gram-negative and decomposed UFAs through decarboxylation, hydroxylation, and hydroperoxidation mechanisms. Received: 3 November 1998 / Accepted: 30 November 1998     

Detection of Mitochondrial COII DNA Sequences in Ant Guts as a Method for Assessing Termite Predation by Ants

Termites and ants contribute more to animal biomass in tropical rain forests than any other single group and perform vital ecosystem functions. Although ants prey on termites, at the community level the linkage between these groups is poorly understood. Thus, assessing the distribution and specificity of ant termitophagy is of considerable interest. We describe an approach for quantifying ant-termite food webs by sequencing termite DNA (cytochrome c oxidase subunit II, COII) from ant guts and apply this to a soil-dwelling ant community from tropical rain forest in Gabon. We extracted DNA from 215 ants from 15 species. Of these, 17.2 % of individuals had termite DNA in their guts, with BLAST analysis confirming the identity of 34.1 % of these termites to family level or better. Although ant species varied in detection of termite DNA, ranging from 63 % (5/7; Camponotus sp. 1) to 0 % (0/7; Ponera sp. 1), there was no evidence (with small sample sizes) for heterogeneity in termite consumption across ant taxa, and no evidence for species-specific ant-termite predation. In all three ant species with identifiable termite DNA in multiple individuals, multiple termite species were represented. Furthermore, the two termite species that were detected on multiple occasions in ant guts were in both cases found in multiple ant species, suggesting that ant-termite food webs are not strongly compartmentalised. However, two ant species were found to consume only Anoplotermes-group termites, indicating possible predatory specialisation at a higher taxonomic level. Using a laboratory feeding test, we were able to detect termite COII sequences in ant guts up to 2 h after feeding, indicating that our method only detects recent feeding events. Our data provide tentative support for the hypothesis that unspecialised termite predation by ants is widespread and highlight the use of molecular approaches for future studies of ant-termite food webs.     

Bromate Reduction by Denitrifying Bacteria

In the presence of bromide, ozonation as applied in water treatment results in the formation of bromate, an ion with carcinogenic properties. The reduction of bromate by mixed bacterial populations as well as pure cultures was studied under laboratory conditions. Bromate was reduced to bromide by a mixed bacterial population with and without a preceding nitrate reduction step in an anaerobically incubated medium with ethanol as the energy and carbon source at 20 and 25 deg C. The predominating bacteria isolated from the batches showing bromate reduction were identified as Pseudomonas spp. Strains of Pseudomonas fluorescens reduced BrO(inf3)(sup-) to Br(sup-) but at a much lower rate than the mixed bacterial population did. Nitrate is a preferred electron acceptor for the bromate-reducing bacteria. Bromate reduction did not occur in the presence of NO(inf3)(sup-), and the rate of bromate reduction was at least 100 times lower than the rate of nitrate reduction. Bromate was completely converted to Br(sup-), indicating that intermediates, e.g., BrO(inf2)(sup-), did not accumulate during bromate reduction.     

Presence of Novel,Potentially Homoacetogenic Bacteria in the Rumen as Determined by Analysis of Formyltetrahydrofolate Synthetase Sequences from Ruminants

Homoacetogens produce acetate from H₂ and CO₂ via the Wood-Ljungdahl pathway. Some homoacetogens have been isolated from the rumen, but these organisms are expected to be only part of the full diversity present. To survey the presence of rumen homoacetogens, we analyzed sequences of formyltetrahydrofolate synthetase (FTHFS), a key enzyme of the Wood-Ljungdahl pathway. A total of 275 partial sequences of genes encoding FTHFS were PCR amplified from rumen contents of a cow, two sheep, and a deer. Phylogenetic trees were constructed using these FTHFS gene sequences and the translated amino acid sequences, together with other sequences from public databases and from novel nonhomoacetogenic bacteria isolated from the rumen. Over 90% of the FTHFS sequences fell into 34 clusters defined with good bootstrap support. Few rumen-derived FTHFS sequences clustered with sequences of known homoacetogens. Conserved residues were identified in the deduced FTHFS amino acid sequences from known homoacetogens, and their presence in the other sequences was used to determine a “homoacetogen similarity” (HS) score. A homoacetogen FTHFS profile hidden Markov model (HoF-HMM) was used to assess the homology of rumen and homoacetogen FTHFS sequences. Many clusters had low HS scores and HoF-HMM matches, raising doubts about whether the sequences originated from homoacetogens. In keeping with these findings, FTHFS sequences from nonhomoacetogenic bacterial isolates grouped in these clusters with low scores. However, sequences that formed 10 clusters containing no known isolates but representing 15% of our FTHFS sequences from rumen samples had high HS scores and HoF-HMM matches and so could represent novel homoacetogens.Feed ingested by ruminant animals is fermented in the rumen by a complex community of microbes. This community produces, among other products, the volatile fatty acids acetate, propionate, and butyrate, which are absorbed across the rumen wall and satisfy a large part of the animals'' carbon and energy requirements. Hydrogen gas (H₂) is also formed and is the major precursor of the methane (CH₄) formed in ruminant animals. This ruminant-derived CH₄ is a contributor to global greenhouse gas emissions (46) and also represents an energy loss for the animals (34). Proposed ruminant greenhouse gas mitigation strategies include using feeds that produce less CH₄ and more volatile fatty acids (31). Alternative strategies include interventions that slow or halt methanogenesis by vaccination, using natural inhibitors found in plants, and supplementing feed with fats and oils or small-molecule inhibitors (31, 32). In the absence of methanogenesis, accumulation of H₂ could lead to a decrease in the rate of feed fermentation (31, 53) and hence a decrease in animal productivity. Other microbes that use H₂ without producing methane could be valuable in conjunction with intervention strategies that inhibit methanogens. This possibility has sparked interest in possible inoculation of ruminants with alternative H₂ users.Bacteria that use the Wood-Ljungdahl pathway to produce acetate from CO₂ are metabolically (6) and phylogenetically (48) diverse and are designated “homoacetogens.” Homoacetogens grow with H₂ or other suitable electron donors, such as formate or sugars, plus CO₂ as a terminal electron acceptor, heterotrophically with organic substrates such as sugars and methoxylated compounds, or mixotrophically with, e.g., H₂ and organic substrates. Homoacetogens have been reported to occur in a normally functioning rumen, but they are unlikely to compete with methanogens for H₂ (24, 25, 34). However, homoacetogens could play an important role in the disposal of H₂ if methanogens are not established in or are eliminated from the rumen (11, 17). At present, it is not clear whether resident rumen homoacetogens could fulfill the H₂ disposal role or whether homoacetogens would have to be added to the rumen to take over this role from the methanogens.Cultivation-based enumeration techniques have shown that the sizes of rumen acetogen populations range from undetectable to 1.2 × 10⁹ per g of rumen contents and that the prevalence of these acetogens depends on diet, animal age, and time of sampling (5, 7, 23, 24). Several homoacetogens, including Acetitomaculum ruminis (15), Eubacterium limosum (14, 17), Blautia schinkii, and Blautia producta (11), have been isolated from ruminants. Homoacetogens have also been isolated from the kangaroo forestomach, whose function is analogous to that of the rumen, which suggests that homoacetogenesis may play a role in hydrogen removal in the low-methane-emission forestomach (37).Because homoacetogens occur in different lineages of bacteria (48), traditional 16S rRNA gene-based surveys provide little information on their prevalence. The formyltetrahydrofolate synthetase (FTHFS) gene (fhs) has been used as a functional marker for homoacetogens, as the enzyme that it encodes catalyzes a key step in the reductive acetogenesis pathway (26). The structure of the enzyme of the homoacetogen Moorella thermoacetica has been reported, and putative functional features have been identified (27, 41, 42). FTHFS sequences from true homoacetogens differ from their homologs in sulfate-reducing bacteria and in other bacteria that degrade purines and amino acids via the glycine synthase-glycine reductase pathway (12, 21, 22, 26). At present, only a limited number of FTHFS sequences have been deposited in databases, and the vast majority of them are partial sequences retrieved from complex microbial communities. FTHFS sequences have been surveyed in sludge (39, 43, 54), termites (40, 44), salt marsh plant roots (21), horse manure (22), cow manure, freshwater sediment, rice field soil, and sewage (54), but so far only one study has investigated bovine ruminal FTHFS sequences (30). The rumen FTHFS sequences had low levels of similarity to the FTHFS sequences of known homoacetogens and could be sequences of novel homoacetogens. To our knowledge, no bacteria with these unique FTHFS sequences have been identified.The aims of this study were to assess the diversity of FTHFS gene sequences retrieved from rumen samples and to screen novel rumen isolates for the presence of FTHFS genes and test their ability to grow as homoacetogens. We used alignments of FTHFS sequences to define a homoacetogen similarity score based on the presence of diagnostic amino acids and developed a hidden Markov model to assess the likelihood that FTHFS sequences of unknown origin are sequences from true homoacetogens that are able to use H₂ or alternative electron donors for reductive acetogenesis.     

Oxygen Reduction Reaction Affected by Sulfate-Reducing Bacteria: Different Roles of Bacterial Cells and Metabolites

Sulfate-reducing bacteria (SRB) were found to be capable of tolerating a certain amount of oxygen (O₂), but how they affect oxygen reduction reaction (ORR) has not been clear. The present work investigated the impact of SRB on ORR in 3.5 wt% sodium chloride solution with the cyclic voltammetry method. The addition of SRB culture solution hampered both the reduction of O₂ to superoxide (O ₂ ^·? ) and hydrogen peroxide (H₂O₂) to water (H₂O), and the influence of SRB metabolites was much larger than that of bacterial cells. Sulfide and extracellular polymeric substances (EPS), typical inorganic and organic metabolic products, had great impact on ORR. Sulfide played an important role in the decrease of cathodic current for H₂O₂ reduction due to its hydrolysis and chemical reaction activity with H₂O₂. EPS were sticky, easy to adsorb on the electrode surface and abundant in functional groups, which hindered the transformation of O₂ into O ₂ ^·? and favored the reduction of H₂O₂ to H₂O.     

甘草内生细菌多样性研究

以分离培养的方法对内蒙古鄂尔多斯市甘草基地野生及栽培甘草内生细菌的多样性进行了初步研究。结果表明, 野生及栽培甘草植株内存在大量种群丰富的内生细菌。经ERIC-PCR指纹图谱分析, 共分离到120株内生细菌, 野生及栽培甘草均表现出根和叶部位的内生细菌数量多于茎部。对其中82株进行16S rDNA片段测序分析, 结果表明这些内生细菌分别与GenBank中α、β、γ-Proteobacteria、Firmicutes、Actinobacteria五类细菌中的19个已知属相似性达到97％～100%。内生细菌的主要优势种群为芽孢杆菌属(Bacillus sp.)、假单胞菌属(Pseudomonas sp.)、泛菌属( Pantoea sp.)和沙雷氏菌属(Serratia sp.)。     

Properties of Bacteria Isolated from Deep-Sea Sediments

Thirty-eight isolates were subjected to taxonomic analysis by computer. Of the 38 isolates, 31 were from sediment samples collected at depths from 9,400 to 10,400 meters in the Philippine and Marianas Trenches of the Pacific Ocean, and 7 cultures were from seawater samples collected at various depths from surface to 4,000 meters and from several locations in the Pacific Ocean. A total of 116 characteristics were determined for each isolate, coded, and transferred to punch cards. Similarity values were obtained by computer analysis, with the use of two recently developed computer programs. Five distinct phenetic clusters were observed from the numerical analyses. Four of the clusters were identified as species of the genus Pseudomonas, and one, as an aerogenic species of Aeromonas. Group IV was identified as pigmented Pseudomonas fluorescens, and the major cluster, consisting of groups I and II, which merged at a species level of similarity, was treated as a new species of Pseudomonas. The 38 strain data were compared with data for 132 marine and nonmarine strains previously subjected to computer taxonomic analysis. The barotolerant deep-sea strains, with the exception of the deep-sea P. fluorescens isolates, clustered separately from all other marine strains.     

甘草内生细菌多样性研究

以分离培养的方法对内蒙古鄂尔多斯市甘草基地野生及栽培甘草内生细菌的多样性进行了初步研究.结果表明,野生及栽培甘草植株内存在大量种群丰富的内生细菌.经ERIC-PCR指纹图谱分析,共分离到120株内生细菌,野生及栽培甘草均表现出根和叶部位的内生细菌数量多于茎部.对其中82株进行16S rDNA片段测序分析,结果表明这些内生细菌分别与GenBank中α、β、γ-Proteobacteria、Firmicutes、Actinobacteria五类细菌中的19个已知属相似性达到97%～100%.内生细菌的主要优势种群为芽孢杆菌属(Bacillus sp.)、假单胞菌属(Pseudomonas sp.)、泛菌属(Pantoea sp.)和沙雷氏菌属(Serratia sp.).