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1.
Zilouei H Soares A Murto M Guieysse B Mattiasson B 《Applied microbiology and biotechnology》2006,72(3):591-599
Two reactors, initially operated at 14 and 23±1°C (RA and RB, respectively), were inoculated with a bacterial consortium enriched and acclimatized to the respective temperatures over 4 months. The biofilms, formed in the reactors, were studied using scanning electron microscopy, cultivation of the biofilm microflora, and physiological analysis of the isolates. Two bacteria able to mineralize chlorophenols under a large range of temperature (10–30°C) were isolated from the biofilm communities of reactors RA and RB and characterized as Alcaligenaceae bacterium R14C4 and Cupriavidus basilensis R25C6, respectively. When temperature was decreased by 10°C, the chlorophenols removal capacity was reduced from 51.6 to 22.8 mg l−1 h−1 in bioreactor RA (from 14 to 4°C) and from 59.3 to 34.7 mg l−1 h−1 in bioreactor RB (from 23±1 to 14°C). Fluorescence in situ hybridization (FISH) of the biofilm communities showed that, in all temperatures tested, the β-proteobacteria were the major bacterial community (35–47%) followed by the γ-proteobacteria (12.0–6.5%). When the temperature was decreased by 10°C, the proportions of γ-proteobacteria and Pseudomonas species increased significantly in both microbial communities. 相似文献
2.
Diversity and distribution of alkaliphilic psychrotolerant bacteria in the Qinghai–Tibet Plateau permafrost region 总被引:1,自引:0,他引:1
Zhang G Ma X Niu F Dong M Feng H An L Cheng G 《Extremophiles : life under extreme conditions》2007,11(3):415-424
The Qinghai–Tibet Plateau represents a unique permafrost environment, being a result of high elevation caused by land uplift.
And the urgency was that plateau permafrost was degrading rapidly under the current predicted climatic warming scenarios.
Hence, the permafrost there was sampled to recover alkaliphilic bacteria populations. The viable bacteria on modified PYGV
agar were varied between 102 and 105 CFU/g of dry soil. Forty-eight strains were gained from 18 samples. Through amplified ribosomal DNA restriction analysis (ARDRA)
and phylogenetic analyses, these isolates fell into three categories: high G + C gram positive bacteria (82.3%), low G + C
gram positive bacteria (7.2%), and gram negative α-proteobacteria (10.5%). The strains could grow at pH values ranging from
6.5 to 10.5 with optimum pH in the range of 9–9.5. Their growth temperatures were below 37°C and the optima ranging from 10
to 15°C. All strains grew well when NaCl concentration was below 15%. These results indicate that there are populations of
nonhalophilic alkaliphilic psychrotolerant bacteria within the permafrost of the Qinhai-Tibet plateau. The abilities of many
of the strains to produce extracellular protease, amylase and cellulase suggest that they might be of potential value for
biotechnological exploitation. 相似文献
3.
Bacterial communities in two shallow eutrophic aquatic ecosystems (eastern China) were studied using culture-dependent methods,
and their correlations with the other water parameters were analyzed. Although the values of the comprehensive trophic state
index in Xizi Lake and Hangzhou Canal were almost identical, the abundances of cultivable bacterial communities, such as protein-hydrolyzing
bacteria (PHB), fecal coliforms (FC), nitrogen-utilizing bacteria, phosphate-mineralizing bacteria, and cellulose-decomposing
bacteria (CDB), differed significantly. They were much less in Xizi Lake than in Hangzhou Canal. Correlation analyses indicated
that the abundances of physiological groups of bacteria were determined mainly by the biomasses of phytoplankton and zooplankton,
rather than by the utilized substrates. Xizi Lake was an algae-dominated aquatic ecosystem, a situation that mainly arose
from the influx of inorganic nutrients, and the Hangzhou Canal was bacteria-dominated due to the influx of organic sewage.
Molecular characterization and phylogenetic analysis of isolates showed that there were 6 phylogenetic lineages out of 15
isolates screened from Xizi Lake, including γ-proteobacteria (5), β-proteobacteria (3), α-proteobacteria (2), actinobacteria
(1), firmicutes (4), and bacteroidetes (1). While in Hangzhou Canal there were only 4 bacterial groups among 22 isolates,
γ-proteobacteria comprised about 82%, α-proteobacteria made up 9%, firmicutes and bacteroidetes made up only 4.5%, respectively,
and no β-proteobacteria were found. Enterobacteriaceae were the principal bacteria components in the two aquatic ecosystems,
especially in the sewage-polluted Hangzhou Canal. It can be concluded preliminarily that the bacterial diversity in Xizi Lake
is richer than that in Hangzhou Canal.
Handling editor: J. Padisak 相似文献
4.
Effect of sample handling on estimation of bacterial diversity in marine sediments by 16S rRNA gene sequence analysis 总被引:7,自引:0,他引:7
Paul A. Rochelle Barry A. Cragg John C. Fry R. John Parkes rew J. Weightman 《FEMS microbiology ecology》1994,15(1-2):215-225
Abstract The diversity of bacterial communities in deep marine sediments, up to 503 metres below the sea floor of the Japan Sea, was investigated by sequence analysis of amplified 16S rRNA genes. The use of different sample handling procedures greatly affected the types and diversity of sequences obtained. DNA from sediment samples stored aerobically for up to 24 h before freezing was dominated by sequences belonging to the β- and γ-proteobacteria, many of which appeared to originate from aerobic bacteria. Sub-samples equilibrated anaerobically at 16°C, were then injected with a radiotracer and immediately frozen, to simulate the conditions of a typical control sample from a radiotracer based activity assay, contained mostly α-proteobacterial sequences. Pristine sediment samples taken anaerobically and frozen within 2 h contained the widest diversity of sequences from α-, γ-, δ-proteobacteria and Gram-positive bacteria, which appeared to have originated from predominantly anaerobic or facultative bacteria. It was clear that both samples that were not frozen immediately (within 2 h) showed signs of enrichment of specific bacterial groups. Our results strongly suggest that immediate freezing should always be employed when sediment samples are to be used to assess bacterial diversity by molecular methods. 相似文献
5.
Lasiurus sindicus is a highly nutritive, drought-tolerant, perennial grass that is endemic to the Thar Desert of Rajasthan, India. Analysis
of 16S rRNA coding genes of the bacterial isolates enriched in nitrogen-free semisolid medium, from the surface-sterilized
roots of L. sindicus, showed predominance of Gram-negative over Gram-positive bacteria. According to comparative sequence analysis of 16S rDNA
sequence data, Gram-positive bacteria with low GC content (Staphylococcus warneri and Bacillus sp.) and high GC content (Micrococcus luteus, Microbacterium sp.) were identified. Gram-negative bacteria included Azospirillum sp., Rhizobium sp., Agrobacterium tumefaciens, and Inquilinus limosus (α-proteobacteria); Ralstonia sp., Variovorax paradoxus, and Bordetella petrii (β-proteobacteria); and Pseudomonas pseudoalcaligenes, Stenotrophomonas sp. (γ-proteobacteria). The occurrence of nifH sequences in Azospirillum sp., Rhizobium sp., and P. pseudoalcaligenes showed the possibility of supplying biologically fixed nitrogen by the root-associated diazotrophs to the host plant. 相似文献
6.
Phosphobacteria are able to enhance phosphorus availability in soil and improve crop yields. To develop such biofertilizers,
14 predominant phosphobacteria were isolated from eutrophic aquatic ecosystems. Molecular identification and phylogenetic
analysis revealed three groups among the nine isolates of inorganic phosphate-solubilizing bacteria (IPSB): IPSBl and IPSB2
belonged to the actinobacteria and flavobacteria, respectively, and the other seven belonged to the γ-proteobacteria. Among
five isolates of organic phosphorus-mineralizing bacteria (OPMB), two groups were present: OPMB1 and OPMB3 belonged to the
β-proteobacteria, while the other three belonged to the γ-proteobacteria. The IPSB isolates released 62.8–66.7 mg P 1−1 from tricalcium phosphate under shaking conditions, and 26.8 to 43.7 mg P 1−1 under static conditions; the OPMB strains released 23.5–30.2 mg P 1−1 from lecithin under shaking conditions, and 16.7–27.6 mg P 1−1 under static conditions. To the best of our knowledge, this is the first report indicating that IPSBl (designated Aureobacterium resistents) as a tricalcium phosphate-solubilizing bacterium and OPMB1 and OPMB3 (designated Acidovorax temperans and Achromobacter xylosoxidans, respectively) are lecithin-mineralizing bacteria. This investigation demonstrated that a eutrophic aquatic ecosystem is
a selective source of phosphobacteria and the screened phosphobacteria are a potential alternative to the development of biofertilizers. 相似文献
7.
Yasmin J. Cardoza Archana Vasanthakumar Alonso Suazo & Kenneth F. Raffa 《Entomologia Experimentalis et Applicata》2009,131(2):138-147
In a recent study, we reported a previously undescribed behavior in which a bark beetle exuded oral secretions containing bacteria that have antifungal properties, and hence defend their galleries against pervasive antagonistic Hyphomycete fungi. Actinobacteria, a group known for their antibiotic properties, were the most effective against fungi that invade the spruce beetle galleries. In the present study, we describe the isolation and identification of microorganisms from oral secretions of three bark beetles (Coleoptera: Curculionidae: Scolytinae): the spruce beetle, Dendroctonus rufipennis Kirby, the mountain pine beetle, Dendroctonus ponderosae Hopkins, and the pine engraver, Ips pini Say. Bacteria isolated from these three species span the major bacterial classes α-, β-, and γ-Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, except for D. ponderosae , which yielded no α-proteobacteria or Bacteroidetes isolates. Spruce beetles and pine engraver beetles had similar numbers of α-proteobacteria isolates, but pine engravers yielded twice as many Bacteroidetes isolates as spruce beetles. In contrast, mountain pine beetles yielded more isolates in the β- and γ-proteobacteria than spruce beetles and pine engravers. The highest percentage of Actinobacteria was obtained from spruce beetles, followed by pine engravers and mountain pine beetles. All of the fungal isolates obtained from the three beetle species were Ascomycetes. The greatest fungal diversity was obtained in spruce beetles, which had nine species, followed by pine engravers with five, and mountain pine beetles with one. 相似文献
8.
Psychrotrophic bacteria are known to occur in temperate, constantly cold, and artificially cooled environments. This is the
first report of their occurrence in a constantly warm (ca. 24°–35°C) tropical environment. Soil samples taken from two sites
along the southeastern coastal zone of Jamaica yielded growth of psychotrophic bacteria after 3–4 weeks of enrichment culture
in 1/30 strength tryptic soy broth, 20 mg L−1 cycloheximide at 2°C. Growth of individual isolates at 2°C was confirmed. Isolates include aerobic and fermentative Gram-negative
rods and sporeforming (Bacillus sp.) and non-sporeforming (Aureobacterium sp.) Gram-positive rods. We determined the effect of temperature on growth rate in four isolates. Strain Y1 has an unusually
wide temperature range for growth, 2°–44°C, resembling that of Listeria monocytogenes. In strain R1 the optimum temperature for growth occurred unusually near the maximum temperature for growth. Strains R2 and
Y2 displayed cardinal temperatures typical of known psychotrophs but appear to have evolved enhanced growth potential near
the optimum temperature in response to a constantly warm environment.
Received: 30 April 1997 / Accepted: 9 August 1997 相似文献
9.
Comparison of partial 16S rRNA gene sequences obtained from activated sludge bacteria 总被引:4,自引:0,他引:4
E. J. Vainio A. Moilanen T. T. Koivula D. H. Bamford J. Hantula 《Applied microbiology and biotechnology》1997,48(1):73-79
The cultivated and uncultivated bacterial communities of an activated sludge plant were studied. Two samples were taken and
a total of 516 bacterial isolates were classified into groups using their whole-cell protein patterns. The distribution of
bacteria into protein-pattern groups differed significantly between the two samples, suggesting variation in culturable bacterial
flora. Partial 16S rRNA gene sequences were determined for representatives of the commonest protein-pattern groups. Most of
the sequences obtained were previously unknown, but relatively closely related to known sequences of organisms belonging to
the α, β or γ subclasses of the proteobacteria, the first two subclasses being predominant. This classification of bacteria
isolated on a diluted nutrient-rich medium differed from recent culture-dependent studies using nutrient-rich media. The uncultivated
bacterial community was studied by analyzing ten partial 16S rRNA gene sequences cloned directly from activated sludge. None
of the cloned sequences was identical to those determined for culturable organisms; or to those in the GenBank database. They
were, however, related to the α or β subclasses of the proteobacteria, or to the gram-positive bacteria with a high G+C DNA
content.
Received: 4 November 1996 / Received revision: 24 February 1997 / Accepted: 28 February 1997 相似文献
10.
R. Özkanca 《International microbiology》2002,5(3):127-132
β-Galactosidase activity of Escherichia coli was investigated in response to long-term starvation, changes in temperature and the presence of certain nutrient sources
in lake water. β-Galactosidase activity decreased markedly in filtered-autoclaved lake water at 25 °C and 37 °C, whereas it
remained almost constant at 4 °C and 15 °C for 60 days. Increases in β-galactosidase activity were observed in response to
the following nutrient sources: glycine, serine, methionine and ammonium sulfate at 4 °C; glycine and ammonium sulfate at
15 °C; glycine, serine, methionine and ammonium sulfate at 30 °C. Glycine addition led to an increase in β-galactosidase activity
of almost five and seven orders of magnitude at 15 °C and 30 °C, respectively. In addition, L-methionine had the strongest influence on β-galactosidase activity, which was detected as an increase of seven and eleven
orders of magnitude at 4 °C and 30 °C, respectively. The effect of several amino acids and other nitrogen sources depended
on the concentration of the nutrient source and the temperature. The results showed that, in lake water, long-term starvation,
temperature change, and variations in nitrogen sources alter β-galactosidase activity. Those effects should be taken into
account when monitoring coliforms from the environment.
Electronic Publication 相似文献
11.
Gutless tube-dwelling worms of pogonophorans (also known as frenulates) and vestimentiferans depend on primary production
of endosymbiotic bacteria. The endosymbionts include thiotrophs that oxidize sulfur for autotrophic production and methanotrophs
that oxidize and assimilate methane. Although most of the pogonophoran and vestimentiferan tube worms possess single thiotrophic
16S rRNA genes (16S rDNA) related to γ-proteobacteria, some pogonohorans are known to bear single methanotroph species or
even dual symbionts of thiotrophs and methanotrophs. The vestimentiferan Lamellibrachia sp. L1 shows symbiotic 16S rDNA sequences of α-, β-, γ-, and ε-proteobacteria, varying among specimens, with RuBisCO form
II gene (cbbM) sequences related to β-proteobacteria. An unidentified pogonophoran from the world’s deepest cold seep, 7326-m deep in the
Japan Trench, hosts a symbiotic thiotroph based on 16S rDNA with the RuBisCO form I gene (cbbL). In contrast, a shallow-water pogonophoran (Oligobrachia mashikoi) in coastal Japan Sea has a methanotrophic 16S rDNA and thiotrophic cbbL, which may suggest the feature of type X methanotrophs. These observations demonstrate that pogonophoran and vestimentiferan
worms have higher plasticity in bacterial symbioses than previously suspected. 相似文献
12.
Yuan T Yang P Wang Y Meng K Luo H Zhang W Wu N Fan Y Yao B 《Biotechnology letters》2008,30(2):343-348
A genomic DNA library screen yielded the nucleotide sequence of a 12 kb fragment containing a gene (2067 bp) coding a thermostable
β-galactosidase from Alicyclobacillus acidocaldarius ATCC 27009. The β-galactosidase gene was expressed in Pichia pastoris, and up to 90 mg recombinant β-galactosidase/l accumulated in shake flask cultures. Using o-nitrophenyl-β-d-galactopyranoside as a substrate, the optimum pH and temperature of the purified recombinant β-galactosidase were 5.8–6.0
and 70°C, respectively. The enzyme retained 90% of its activity when heated at 70°C for 30 min. Approximately 48% of lactose
in milk was hydrolyzed following treatment with the recombinant enzyme over 60 min at 65°C. 相似文献
13.
Ashraf Sabry Abdel Fatah El Sayed Shino Fujimoto Chiaki Yamada Hideyuki Suzuki 《Biotechnology letters》2010,32(12):1877-1881
The optimal reaction conditions for the synthesis of γ-glutamylglutamine using γ-glutamyltranspeptidase from Escherichia coli were determined. The maximum yield of γ-glutamylglutamine (110 mM) was obtained using 250 mM l-glutamine and 1.1 U γ-glutamyltranspeptidase/ml at pH 10.5 and at 37°C for 7 h; the conversion of glutamine to γ-glutamylglutamine
was 88%. 相似文献
14.
The gram-negative bacterium Myxobacter sp. AL-1 produces chitosanase-cellulase activity that is maximally excreted during the stationary phase of growth. Carboxymethylcellulase
zymogram analysis revealed that the enzymatic activity was correlated with two bands of 32 and 35 kDa. Ion-exchange-chromatography-enriched
preparations of the 32-kDa enzyme were capable of degrading the cellulose fluorescent derivatives 4-methylumbelliferyl-β-d-cellobioside and 4-methylumbelliferyl-β-d-cellotrioside. These enzymatic preparations also showed a greater capacity at 70° C than at 42° C to degrade chitosan oligomers
of a minimum size of six units. Conversely, the β-1,4 glucanolytic activity was more efficient at attacking carboxymethylcellulose
and methylumbelliferyl-cellotrioside at 42° C than at 70° C. The 32-kDa enzyme was purified more than 800-fold to apparent
homogeneity by a combination of ion-exchange and molecular-exclusion chromatography. Amino-terminal sequencing indicated that
mature chitosanase-cellulase shares more than 70% identity with endocellulases produced by strains DLG, PAP115, and 168 of
the gram-positive microorganism Bacillus subtilis.
Received: 6 January 1997 / Accepted: 29 May 1997 相似文献
15.
Joshi AA Kanekar PP Kelkar AS Shouche YS Vani AA Borgave SB Sarnaik SS 《Microbial ecology》2008,55(2):163-172
Aerobic, alkaliphilic bacteria were isolated and characterized from water and sediment samples collected in the winter season,
January 2002 from alkaline Lonar lake, India, having pH 10.5. The total number of microorganisms in the sediment and water
samples was found to be 102–106 cfu g−1 and 102–104 cfu ml−1, respectively. One hundred and ninety-six strains were isolated using different enrichment media. To study the bacterial
diversity of Lonar lake and to select the bacterial strains for further characterization, screening was done on the basis
of pH and salt tolerance of the isolates. Sixty-four isolates were subjected to phenotypic, biochemical characterization and
16S rRNA sequencing. Out of 64, 31 bacterial isolates were selected on the basis of their enzyme profile and further subjected
to phylogenetic analysis. Phylogenetic analysis indicated that most of the Lonar lake isolates were related to the phylum
Firmicutes, containing Low G+C, Gram-positive bacteria, with different genera: Bacillus, Paenibacillus, Alkalibacillus, Exiguobacterium, Planococcus, Enterococcus and Vagococcus. Seven strains constituted a Gram-negative bacterial group, with different genera: Halomonas, Stenotrophomonas and Providencia affiliated to γ-Proteobacteria, Alcaligenes to β-Proteobacteria and Paracoccus to α-Proteobacteria. Only five isolates were High G+C, Gram-positive bacteria associated with phylum Actinobacteria, with
various genera: Cellulosimicrobium, Dietzia, Arthrobacter and Micrococcus. Despite the alkaline pH of the Lonar lake, most of the strains were alkalitolerant and only two strains were obligate alkaliphilic.
Most of the isolates produced biotechnologically important enzymes at alkaline pH, while only two isolates (ARI 351 and ARI
341) showed the presence of polyhydroxyalkcanoate (PHA) and exopolysaccharide (EPS), respectively. 相似文献
16.
Phylogenetic diversity of bacteria isolates from the Qinghai-Tibet Plateau permafrost region 总被引:3,自引:0,他引:3
Zhang G Niu F Ma X Liu W Dong M Feng H An L Cheng G 《Canadian journal of microbiology》2007,53(8):1000-1010
The Qinghai-Tibet Plateau in east Asia is a unique and important permafrost environment. However, its microbiology remains largely unexplored to date. In this study, sediment samples were collected from the Qinghai-Tibet Plateau permafrost region, bacteria isolation procedures were performed 8 times, and the samples incubated at 4 degrees C for nearly 3 months. The number of colony forming units (cfu) ranged from 0 to 10(7)/(g dry soil). The quantity of culturable bacteria grew exponentially within the first few weeks, and then slowed gradually to a plateau. Phylogenetic analyses indicated that all the isolates fell into 6 categories: high G+C Gram-positive bacteria, low G+C Gram-positive bacteria, alpha-Proteobacteria, beta-Proteobacteria, gamma-Proteobacteria, and Cytophaga-Flavobacterium-Bacteroides group bacteria. The isolates belong to 19 genera, but the genera Arthrobacter and Pseudomonas were predominant. With the increase in incubation time, the isolated populations changed in terms of both species and their respective quantities. Of the 33 analyzed isolates, 9 isolates related to 8 genera might be new taxa. These results suggest that the Qinghai-Tibet Plateau permafrost region is a specific ecologic niche that accommodates an original microbial assemblage. 相似文献
17.
Several molecular techniques were employed to document the bacterial diversity associated with the marine sponge Gelliodes carnosa. Cultivation-dependent and cultivation-independent methods were used to obtain the 16S rRNA gene sequences of the bacteria.
Phylogenetic analysis based on the 16S rRNA gene sequences showed that the bacterial community structure was highly diverse
with representatives of the high G + C Gram-positive bacteria, cyanobacteria, low G + C Gram-positive bacteria, and proteobacteria
(α-, β-, and γ-), most of which were also found in other marine environments, including in association with other sponges. Overall,
300 bacterial isolates were cultivated, and a total of 62 operational taxonomic units (OTUs) were identified from these isolates
by restriction fragment length polymorphism (RFLP) analysis and DNA sequencing of the 16S rRNA genes. Approximately 1,000
16S rRNA gene clones were obtained by the cultivation-independent method. A total of 310 clones were randomly selected for
RFLP analysis, from which 33 OTUs were acquired by further DNA sequencing and chimera checking. A total of 12 cultured OTUs
(19.4% of the total cultured OTUs) and 13 uncultured OTUs (39.4% of the total uncultured OTUs) had low sequence identity (≤97%)
with their closest matches in GenBank and were probably new species. Our data provide strong evidence for the presence of
a diverse variety of unidentified bacteria in the marine sponge G. carnosa. A relatively high proportion of the isolates exhibited antimicrobial activity, and the deferred antagonism assay showed
that over half of the active isolates exhibited a much stronger bioactivity when grown on medium containing seawater. In addition
to demonstrating that the sponge-associated bacteria could be a rich source of new biologically active natural products, the
results may have ecological implications. This study expands our knowledge of the diversity of sponge-associated bacteria
and contributes to the growing database of the bacterial communities within sponges. 相似文献
18.
Brent C. Christner Ellen Mosley-Thompson Lonnie G. Thompson John N. Reeve 《Environmental microbiology》2001,3(9):570-577
Lake Vostok, the largest subglacial lake in Antarctica, is separated from the surface by ≈ 4 km of glacial ice. It has been isolated from direct surface input for at least 420 000 years, and the possibility of a novel environment and ecosystem therefore exists. Lake Vostok water has not been sampled, but an ice core has been recovered that extends into the ice accreted below glacial ice by freezing of Lake Vostok water. Here, we report the recovery of bacterial isolates belonging to the Brachybacteria , Methylobacterium , Paenibacillus and Sphingomonas lineages from a sample of melt water from this accretion ice that originated 3593 m below the surface. We have also amplified small-subunit ribosomal RNA-encoding DNA molecules (16S rDNAs) directly from this melt water that originated from α- and β-proteobacteria, low- and high-G+C Gram-positive bacteria and a member of the Cytophaga / Flavobacterium / Bacteroides lineage. 相似文献
19.
The RpoS sigma factor in proteobacteria regulates genes in stationary phase and in response to stress. Although of conserved
function, the RpoS regulon may have different gene composition across species due to high genomic diversity and to known environmental
conditions that select for RpoS mutants. In this study, the distribution of RpoS homologs in prokaryotes and the differential
dependence of regulon members on RpoS for expression in two γ-proteobacteria (Escherichia coli and Pseudomonas aeruginosa) were examined. Using a maximum-likelihood phylogeny and reciprocal best hits analysis, we show that the RpoS sigma factor
is conserved within γ-, β-, and δ-proteobacteria. Annotated RpoS of Borrelia and the enteric RpoS are postulated to have separate evolutionary origins. To determine the conservation of RpoS-dependent
gene expression across species, reciprocal best hits analysis was used to identify orthologs of the E. coli RpoS regulon in the RpoS regulon of P. aeruginosa. Of the 186 RpoS-dependent genes of E. coli, 50 proteins have an ortholog within the P. aeruginosa genome. Twelve genes of the 50 orthologs are RpoS-dependent in both species, and at least four genes are regulated by RpoS
in other γ-proteobacteria. Despite RpoS conservation in γ-, β-, and δ-proteobacteria, RpoS regulon composition is subject
to modification between species. Environmental selection for RpoS mutants likely contributes to the evolutionary divergence
and specialization of the RpoS regulon within different bacterial genomes. 相似文献
20.
Exopolysaccharides (EPS) from lactic acid bacteria contribute to specific rheology and texture of fermented milk products
and finds applications even in non-dairy foods and in therapeutics. Box-Behnken model of response surface methodology (RSM)
was employed to formulate the production medium for exopolysaccharide (EPS). FT-IR spectral analysis of the purified EPS from
Lactobacillus plantarum MTCC 9510 revealed prominent characteristic groups corresponding to polyhydric alcohols. The degradation temperature (Td)
of the polysaccharide was found to be 260°C with the help of thermo gravimetric analysis (TGA). Structure elucidation of the
EPS showed that it consists of a trisaccharide repeating unit of α-d-glucose, β-d-glucose and α-d-mannose. 相似文献