


卷 87, 编号 1 (2018)
- 年: 2018
- 文章: 15
- URL: https://journals.rcsi.science/0026-2617/issue/view/9925
Experimental Articles
Inhibitory effect of aminoglycosides and tetracyclines on quorum sensing in Chromobacterium violaceum
摘要
Effect of aminoglycosides (kanamycin, gentamycin, and amikacin) and tetracyclines (tetracycline and doxycycline) on the CviI/CviR two-component quorum sensing mediated with C6-AHL autoinducer in Chromobacterium violaceum ATCC 31532 was studied. All antibiotics showed growth-inhibitory activity against the test strain and violated its density-dependent communication system in sub-inhibitory concentrations, which could be seen as suppression of C6-AHL-dependent violacein biosynthesis. The tested antibiotics exhibited an alternative balance of these activities: a direct antibacterial effect prevailed in tetracyclines, while aminoglycosides inhibited quorum sensing system of C. violaceum ATCC 31532 within a broad concentration range. Sensor strains capable of quantitative detection of C6-AHL and bearing the genes of resistance to aminoglycosides (C. violaceum 026) or tetracyclines (Escherichia coli pAL103) were used to analyze the effect of antibiotics on autoinducer accumulation in the cultivation medium. Aminoglycosides were found to suppress C6-AHL production within a broad concentration range; and therefore quorum sensing in C. violaceum ATCC 31532 did not function because of C6-AHL limitation. The obtained results were analyzed in relation to their biological role in natural microbiocenoses, as well as in relation to antibiotic treatment of bacterial infections caused by organisms using quorum sensing for induction of their pathogenic potential.



Antibiofilm potential of biogenic silver nanoparticles against Kocuria rosea And Kocuria rhizophila
摘要
The present study aims at biosynthesizing, characterizing and evaluating the biogenic silver nanoparticles (AgNPs) as antimicrobial and antibiofilm against Kocuria rosea and Kocuria rhizophila. Cellfree supernatant of Proteus mirabilis culture was used for biosynthesizing AgNPs, which confirmed by visualizing color change and X-ray diffraction. Transmission electron microscopy showed the formation of AgNPs in the range of 5–40 nm. ART-FTIR spectra provided evidence for presence of proteins as possible biomolecules responsible for stability of AgNPs and act as capping agent. AgNPs had ability to inhibit growth of K. rosea and K. rhizophila. The minimum inhibitory concentration (MIC90) of AgNPs against both strains was 25 μg/mL. Antiadhesive effect of AgNPs was verified at sub-MIC90 dose (12.5 μg/mL). The AgNPs concentrations up to 100 μg/mL were not effective for complete removing the already established biofilms with maximum removing percentage of 30.5–34.9%. In conclusion, the present study demonstrated an unprecedented green process for biosynthesizing stable spherical-shaped AgNPs. Early control is suggested by preventing biofilm formation using low AgNPs concentration (12.5 μg/mL) as a potential ingredient for formulating effective chemical sanitizers.



Dynamics of the cytosol soluble carbohydrates and membrane lipids in response to ambient pH in alkaliphilic and alkalitolerant fungi
摘要
Comparative composition of lipids and cytosol soluble carbohydrates at different ambient pH values was studied for two obligately alkaliphilic fungi (Sodiomyces magadii and S. alkalinus) and for two alkalitolerant ones (Acrostalagmus luteoalbus and Chordomyces antarcticus). The differences and common patterns were revealed in responses to pH stress for the fungi with different types of adaptation to ambient pH. While trehalose was one of the major cytosol carbohydrates in alkaliphilic fungi under optimal growth conditions (pH 10.2), pH decrease to 7.0 resulted in doubling its content. In alkalitolerant fungi trehalose was a minor component and its level did not change significantly at different pH. In alkalitolerant fungi, arabitol and mannitol were the major carbohydrate components, with their highest ratio observed under alkaline conditions and the lowest one, under neutral and acidic conditions. In alkaliphiles, significant levels of arabitol were revealed only under alkaline conditions, which indicated importance of trehalose and arabitol for alkaliphily. Decreased pH resulted in the doubling of the proportion of phosphatidic acids among the membrane lipids, which was accompanied by a decrease in the fractions of phosphatidylcholines and sterols. Alkalitolerant fungi also exhibited a decrease in sterol level at decreased pH, but against the background of increased proportion of one of phospholipids. Decreased unsaturation degree in the fatty acids of the major phospholipids was a common response to decreased ambient pH.



Methylophaga muralis Bur 1, a haloalkaliphilic methylotroph isolated from the Khilganta soda lake (Southern Transbaikalia, Buryat Republic)
摘要
A haloalkaliphilic restricted facultative methylotroph, strain Bur 1, which used methanol, methylated amines, and fructose as carbon and energy sources, was isolated from the soda Lake Khilganta (Buryat Republic, Russia). The cells were gram-negative non-spore-forming, motile rods reproducing by binary fission. The organism was aerobic, reduced nitrates to nitrites. Growth occurred at temperatures from 4 to 37°C (optimum at 25–29°C), pH 7.5–10.5 (optimum at 8.5–9.5), and NaCl concentration in the medium from 0.05 to 10.0% NaCl (optimum at 3–4%). Ectoine, glutamate, and sucrose were accumulated as osmoprotectants. Activity of the enzymes of de novo ectoine biosynthesis were detected. The organism utilized C1 compounds via the KDPG variant of the ribulose monophosphate pathway. The DNA G + C content was 44.67 mol %. Based on the similarity of the 16S rRNA gene sequences (94.7–99.1%) and the results of DNA–DNA hybridization (24–74%) with type strains of the neutrophilic and alkaliphilic Methylophaga species, the isolate was identified as Methylophaga muralis Bur 1 (VKM B-3046 = DSM 103617). The genome of M. muralis Bur 1 contained 2585 protein-encoding genes; 634 proteins with unidentified functions were predicted. Three rRNAs (5S, 16S, and 23S) and 38 tRNAs were identified. Apart from the mxaFJGIRSACKLDEH classical cluster of methanol oxidation genes, the xoxF gene was found. Methylamine was oxidized to formaldehyde by methylamine dehydrogenase and via the N-methylglutamate pathway. Orthologs of type III glutamine synthetases were revealed in the genome. The operons of ectoine and sucrose biosynthesis, ectRABC-ask and sps-spp-fruK-ams, were found. The genomes of M. muralis Bur 1 and M. lonarensis MPLT, unlike that of M. nitratireducenticrescens JAM1T, were found to contain the genes encoding the proteins of bicarbonate transport.



Obligate methylotroph Methylobacillus arboreus IvaT synthesizes a plant hormone, gibberellic acid GA3
摘要
An obligate methylotroph Methylobacillus arboreus IvaТ (VKM B-2590Т, CCUG 59684T, DSM 23628T) is the first known aerobic methylotrophic bacterium capable of synthesis of the bioactive gibberellic acid GA3. Primary separation and identification of gibberellic acid from the culture liquid of methanol-grown culture were carried out using thin-layer chromatography and high-performance liquid chromatography. The concentration and structure of the gibberellic acid GA3 were determined by liquid chromatography−mass spectrometry (LC/MS). Biological activity of the isolated compound was confirmed by tests on sprouts of lettuce (Laсtuca sativa L.).



Lipid composition of the spores of zygomycetous and ascomycetous fungi during cessation of the exogenous dormancy state
摘要
The composition of lipids and fatty acids was studied in the spores of exogenously dormant (spores 0) and germinating (spores G) spores in distilled water for sporangiospores of zygomycetous fungi Cunninghamella echinulata VKM F-663 and Umbelopsis ramanniana VKM F-582 and for conidia of ascomycetous fungi Aspergillus tamarii VKM F-64 and A. sydowii VKM F-441. Compared to spores 0, the lipids of spores G contained higher shares of unsaturated fatty acids, lower levels of massive phospholipids (phosphatidylcholine and phosphatidylethanolamine), and elevated levels of phosphatidylglycerol and phosphatidic acid. The level of cardiolipin, the main phospholipid of the mitochondrial membranes, increased when the spores of both zygomycetes exited from the dormant state. While a certain increase in the content of free and esterified sterols in the neutral lipids of the slowly germinating U. ramanniana G spores was observed, germination of sporangiospores and conidia of the studied fungi generally did not result in significant changes in the composition of the neutral lipid classes, which may be due to the fact that they are not the major reserve mobilized at the stage of exit from the dormant state.



Analysis of Congo red-induced changes in the cell surface and macrocolony structure of the bacterium Azospirillum brasilense
摘要
Adsorption of the vital dye Congo red suppresses swarming of Azospirillum brasilense in a semiliquid medium, and the bacteria become able to spread with the formation of microcolonies. By using direct and stereoscopic light microscopy, the patterns of the front of Azospirillum spreading in a semiliquid medium containing the dye were analyzed. It was found that in a medium with Congo red, small motile colonies were formed among the individual cells, and once formed, they left the boundaries of the swarming front. The microcolonies produced by azospirilla in the presence of the dye were ordered bacterial structures, rather than random cell aggregates. Transmission electron microscopy revealed that the cells grown without the dye had polar flagella, whereas the cells from the medium with Congo red had no flagella and were covered with a layer of fibrillike material. Immunochemical data for the cell surface changes resulting from interaction with the dye make it possible to consider Azospirillum lipopolysaccharide as a probable Congo red receptor.



Microbial processes of organic matter production and decomposition in saline rivers of the Lake Elton area (Volgograd oblast, Russia)
摘要
The rates of microbial processes and phylogenetic diversity of the microorganisms responsible for organic matter production and decomposition in the benthic communities and bottom sediments of the rivers Solyanka, Lantsug, Khara, Chernavka, and Bol’shaya Smorogda (Lake Elton area, Volgograd oblast, Russia) were studied. The biomass and primary production of cyano–bacterial communities varied significantly within the ranges of 20–903 mg Chl a/m2 and 0.2–21 mg C/(m2 h), respectively. Depending on the season, the share of anoxygenic CO2 fixation varied from 20% to the values comparable to the rate of oxygenic photosynthesis. The total heterotrophic activity of microbial communities determined as the rate of dark CO2 assimilation varied from 31 to 750 μmol/(dm3 day) in the mats and from 3 to 137 μmol/(dm3 day) in the sediments. The rates of sulfate reduction and hydrogenotrophic methanogenesis varied from 10 to 2621 μmol S/dm3 day) and from 1.5 to 323 nmol CH4/(dm3 day), respectively. High-throughput sequencing of the 16S rRNA genes in cyano–bacterial mats revealed microorganisms belonging to 20 phyla, with the sequences of Cyanobacteria, Proteobacteria, and Bacteroidetes being the most numerous.



Bacterial complexes of Khibiny Mountains lichens revealed in Cladonia uncialis, C. portentosa, Alectoria ochroleuca, and Nephroma arcticum
摘要
Fluorescence in situ hybridization was used to investigate microbial communities of four lichen species collected in the Murmansk province. The maximal bacterial abundance was shown to depend on both the lichen species and the part of the thallus. Predominant groups of bacteria were revealed: Proteobacteria, Acidobacteria, and Actinobacteria. Criteria for assessment the facultative and obligatory presence of bacteria in lichen microbial communities were established, and approaches to classification of the lichen microbial communities were proposed based on the interdependence of various bacterial groups.



Structure of microbial communities of peat soils in two bogs in Siberian tundra and forest zones
摘要
The structure and functional activity of microbial complexes of a forest oligo-mesotrophic subshrub- grass-moss bog (OMB, Central Evenkiya) and a subshrub-sedge bog in the polygonal tundra (PB, Lena River Delta Samoylovsky Island) was studied. Soil of the forest bog (OMB) differed from that of the polygonal tundra bog (PB) in higher productivity (Corg, Ntotal, P, and K reserves), higher biomass of aerobic chemoorganotrophs (2.0 to 2.6 times), and twice the level of available organic matter. The contribution of microorganisms to the carbon pool was different, with the share of Cmic in Corg 1.4 to 2.5 times higher in PB compared to OMB. Qualitative composition of the methane cycle microorganisms in PB and OMB soils differed significantly. Methanogenic archaea (Euryarchaeota) in the shrub-sedge PB of tundra were more numerous and diverse than in the oligo-mesotrophic bog (OMB) and belonged to six families (Methanomassiliicoccaceae, Methanoregulaceae, Methanobacteriaceae, Methanomicrobiaceaee, Methanosarcinaceae, and Methanotrichaceae), while members of only four families (Methanosarcinacea, Methanobacteriaceae, Methanotrichaceae, and Methanomassiliicoccaceae) were revealed in OMB. In both bogs, methane-oxidizing bacteria belonged to Alphaproteobacteria (II) and Gammaproteobacteria (I). Methanotroph diversity was higher in OMB than in PB. Microbial communities of PB soils had higher potential activity of methanogenesis and methanotrophy compared to those of OMB. Methanogenic and methanotrophic activities in PB were 20 and 2.3 times higher, respectively, than in OMB.



Comparative bacterial survey in the gut of lepidopteran insects with different bionetwork
摘要
Insect gut is an untapped reservoir persist numerous unidentified gene responsible for the digestion of complex food material into a simpler nutrients, this activity of gut was enhanced by the microbial interaction. Insect gut-microbe interaction encodes beneficial activity to its host in several aspects, to illuminate the tactic of the interaction this study was framed and worked out in two insect species such as Spodoptera litura and Bombyx mori. The present study surveyed the comparative diversity of microbial population in the gut of a field pest Spodoptera litura and domesticated insect silkworm Bombyx mori at their active feeding larval stage. Both culture dependent and culture independent approaches exposed the dominance of Enterobacteriacae family and with majority of proteobacteria and firmicutes residing in the gut of both Spodoptera litura and Bombyx mori. Especially, the Enterococcus mundtii is a predominant affiliate in both processes of both insects.



Isolation and evaluation of probiotic potential of lactic acid bacteria isolated from poultry intestine
摘要
The gut is a source of lactic acid bacteria with remarkable functional and technologies properties as well as a potential source of probiotics. In the present study, 13 strains of Lactobacillus were isolated from poultry intestine and identified according to their 16S rDNA sequences, as well as the evaluation of their probiotic potential. The probiotic properties were tested in aspects of antibiotic susceptibility, antimicrobial activity, exopolysaccharide production, lysozyme tolerance, gut condition tolerance (low pH, bile salt tolerance) and adhesion to human colorectal adenocarcinoma cell line (Caco-2). Most isolates were resistance to streptomycin (10 μg/mL), gentamicin (10 μg/mL), kanamycin (30 μg/mL), penicillin (10 μg/mL) and chloramphenicol (30 μg/mL). Isolates shows strong abilities to adhere to Caco-2 cell in the range of (76 to 85%). Isolates SHA101 to SHA113 showed high survival rate under gastrointestinal tract condition (>80%), indicating their potential in application of probiotics. The results of these tests indicate that the lactic acid bacteria isolated from poultry intestine have potential use as probiotic in various products.



Phylogeny and genetic diversity assessment of Ensifer strains nodulating Senegalia (Acacia) senegal (L.) Britton. in arid regions of Western Rajasthan, India
摘要
The tree Senegalia (Acacia) senegal is well adapted to soils of arid regions having a vital role in reforestation and increasing soil fertility through biological nitrogen fixation in addition to its utility as edible seeds and gum. Fifty-nine root nodule bacterial (RNB) strains were isolated; characterized at phenotypic and genotypic level; and host range was studied. The Senegalia-RNB strains were able to grow up to 3% NaCl and on a wide range of pH (5–11) with optimum growth at alkaline pH showing their adaptation to alkaline desert soil. The carbon utilization pattern of Senegalia-RNB strains was significantly different from existing closely related type strains of Ensifer. The PCR-RFLP (ARDRA) as well as RAPD patterns revealed considerable genetic diversity among the strains forming distinct genetic groups. The 16S rRNA phylogeny of selected six (AS11, AS18, AS27, AS34, AS50 and AS53) strains showed that they belong to fast growing species of Ensifer with few being similar to the previously described Ensifer strains from Vachellia jacquemontii and Vachellia leucophloea from Thar Desert of India. The symbiotic (nifH and nodA) gene phylogeny showed incongruence with that of 16S rRNA gene (species) phylogeny suggesting HGT incidences under hot-arid and alkaline environment. The Senegalia-Ensifer strains possessing novel symbiotic genes could effectively cross-nodulate species of Vachellia (V. jacquemontii, V. leucophloea and V. nilotica) but failed to nodulate the crop Vigna radiata. Multi locus sequence analysis (MLSA) is required to determine novelty of these Ensifer strains and more cross-inoculation studies will help in understanding their potential use as inoculums in nursery practices for reforestation program in arid and semi-arid regions.



Metagenomic microbial community profiling of Unnai hot spring by Ion-Torrent based shotgun sequencing
摘要
This is the first report on depicting the pioneering microbiota of Unnai hot spring using shotgun metagenome sequencing approach. Community analysis encompassed a total of 688,059 sequences with the total size 125.31 Mbp and 46% G + C content. Sequencing metagenome reported about 992 species belonged to 40 different phyla dominated by Firmicutes (97.49%), Proteobacteria (1.36%), and Actinobacteria (0.31%). In functional analysis, Non-Supervised Orthologous Groups (NOG) annotation revealed the predominance of poorly characterized reads (82.79%). Moreover, the subsystem classification displayed 19% genes assigned to carbohydrates metabolism, 12% genes allocated to clustering-based subsystems, 10% genes belonged to amino acids and its derivatives. The result suggests the huge bacterial diversity which will be useful for further characterizing the economically important bacteria for biotechnological applications.



Short Communications
Cellulosimicrobium sp. strain NPZ-121, a degrader of 2,4,5-trichlorophenoxyacetic acid


