微生物学报最新文献

PhoPR is an important two-component regulatory system in Mycobacterium tuberculosis. PhoP is essential for virulence as a response regulator involved in cell wall lipid biosynthesis and regulation of gene expression. In this review, the structure, function and vaccine application of PhoP were summarized, as well as some questions that need to be solved.

Objective: We studied the interactions in a co-culture of two bacteria.

Methods: By pairwise co-culturing of 36 Escherichia coli and 36 Staphylococcus aureus strains, we monitored the growth of each species in an interaction environment. We identified numerous Single Nucleotide Polymorphisms (SNPs) by whole-genome sequencing used as genetic markers to predict variations in phenotypic traits. Genome-wide association study (GWAS) was applied to identify loci that controlled competition between the two species.

Results: In E. coli, 162 significant SNPs affected the change of maximum growth rate by comparing initials strains with those grown in co-culture, and 36 significant SNPs affected the change of maximum growth rate comparing monoculture and co-culture strains. Five of the significant E. coli genes we identified after annotation this time were also reported in other evolutionary studies. We also identified 85 significant SNPs in S. aureus that affected the change of maximum growth rate by comparing initial strains with those grown in monoculture. About the change of bacterial numbers, we found that 706 significant SNPs were associated in E. coli and 129 in S. aureus. Thirteen of the E. coli significant genes in this study were also verified in previous evolutionary reports

Conclusion: We found several significant genes both in monoculture and co-culture affecting the interaction of E. coli and S. aureus. GWAS has the potential to study interspecific interactions of bacteria.

Understanding the biotransformation mechanism of chlorinated hydrocarbons in contaminated site is of great significance to the in-situ bioremediation. Therefore, we summed up the overlapping composition of chlorinated hydrocarbons and analyzed statistically the concentration variations and degradation rate of chlorinated hydrocarbons in various landfill which were regarded as one of the most typical compound pollution sites. The statistical data indicated that chloralkane and chloroalkene concentration ranged 0.20 to 32.45 and 0.50 to 32.45 μg/m3, respectively, which were the main components. We also found that biodegradation rates of chlorinated hydrocarbons decreased with the number of attached chlorine atoms in landfill cover. Then, we summarized the biodegradation mechanism of chlorinated hydrocarbons under different environmental conditions. The results implied that chlorinated hydrocarbons biodegradation incorporated aerobic co-metabolism, halorespiration and anaerobic reductive dechlorination involved in a wide range of substrates and a variety of functional microbes. Based on of these analyses, we constructed biodegradation models of chlorinated hydrocarbons in landfill cover. Finally, the possible development of chlorinated hydrocarbons biological removal in the future was predicated.

Objective: In addition to Streptococcus suis serotype 2, Streptococcus suis serotype 9 (SS9) is also a currently prevalent serotype and a zoonotic pathogen. In our previous study, SS9 DNA nuclease (SsnA) was considered as a candidate virulence factor. To clarify the impact of SsnA on SS9 virulence, we constructed ssnA mutant (ΔssnA) and studied its biological functions.

Methods: We evaluated the virulence of wild type strain and ΔssnA in a zebrafish infection model and compared the adherence rate to HEp-2 cells, the survival rate in pig blood, and enzymatic activity between wild type stain and ΔssnA.

Results: In a zebrafish infection experiment, the 50% lethal dose value of ΔssnA was 11.2-fold higher than that of wild type strain. The adherence rate of ΔssnA to HEp-2 cells was only 60.61% of the wild strain level. The survival rate of ΔssnA in pig blood was declined to 71.88% of wild strain level. The enzymatic activity assay showed that SsnA can degrade both linear and circular DNA.

Conclusion: SsnA contributes to SS9 virulence in a zebrafish infection model, the adherence to HEp-2 cells, and the survival in pig blood. SsnA is indeed an essential virulence factor for SS9.

Objective: The physiological function of membrane protein RHOGL009301 in Rhodococcus sp. R04 and the metabolic properties of the mutant strain were studied to determine the relationship between the physiological function of the membrane protein and the transport of benzoate.

Methods: The RHOGL009301 gene and the green fluorescent protein gene were fused for expressing in Rhodococcus erythropolis, and the location of RHOGL009301 was observed by Delta Vision. The RHOGL009301 gene was knocked out by homologous recombination, and the growth of wild strain and deficient strain in different carbon sources were compared. The internal and external metabolites of the wild strain and the deficient strain when grown on biphenyl and benzoate were measured by HPLC, and the changes of metabolite concentration in different growth conditions were analyzed.

Results: A fusion gene that contained RHOGL009301 gene and the green fluorescent protein gene was co-expressed in Rhodococcus erythropolis and localized on the cell membrane. The deficient strain R04ΔMP of RHOGL009301 gene was obtained. The biomass of the deficient strain was significantly reduced in biphenyl and benzoate culture, and its growth rate was slowed down. HPLC analysis showed that the deletion of RHOGL009301 gene inhibited the transport of benzoate.

Conclusion: RHOGL009301 membrane protein is one of the proteins involved in metabolism and transport of benzoate. Based on sequence homology analysis, we can conclude that the membrane protein is a novel benzoate transport protein.

Objective: To study the effect of amphipathic helix characteristics of FtsZ (236-245) domain on FtsZ assembly and interaction of FtsZ with FtsA in Escherichia coli strains.

Methods: We constructed FtsZ and its mutant's plasmids by molecular clone and site-directed mutagenesis, and purified targeted proteins using affinity chromatography. QN23-QN29 strains were constructed by linear DNA homologous recombination and P1 transduction. We observed cellular localization patterns of FtsZ and its mutants in E. coli by living cell imaging experiments, examined membrane binding properties of FtsZ mutants by membrane proteins isolation and Western blot analysis, and analyzed interaction of FtsZ/FtsZ* with FtsA by Co-immunoprecipitation and far Western blot. Native gel separation and in vitro polymerization experiments were done to check effects of FtsZ point mutation on FtsZ assembly.

Results: Yfp-labeled FtsZE237A/K and FtsZE241A/K mutant proteins failed to localize in E. coli strains, assemble into functional Z-ring structure, and had decreased function of FtsZ (wt). In vitro experiments showed that E237A/K and E241A/K mutations of FtsZ decreased the polymerization efficiency of FtsZ monomer, weakened FtsZ*-FtsA interaction and changed membrane binding properties of FtsZ.

Conclusion: FtsZ E237 and E241 are critical amino acids that affect the amphipathic helix characteristics of FtsZ (236-245) domain, FtsZ assembly and FtsZ-FtsA interaction in E. coli strains.

Objective: I studied the community structure and diversity of culturable moderate halophilic bacteria isolated from Qrhan Salt Lake.

Methods: I isolated and cultured the moderate halophilic bacteria on different selective media. After the 16S rRNA gene sequences was amplified and measured, I constructed the phylogenic tree, analyzed the community structure and calculated the diversity indexes according to the 16S rRNA gene information.

Results: A total of 421 moderate halophilic bacteria were isolated from water and mud samples in Qrhan Salt Lake. The 16S rRNA gene information showed that 4 potential novel species belonged to the family Bacillaceae. Eighty-three model strains belonged to 3 phylurms 6 families 16 genus. Among them, Bacillus sp., Oceanobacillus sp. and Halomonas sp. were dominant species. Diversity analysis showed that the diversity of strains isolated from water sample was higher than that from mud sample, but the dominance degree of strains isolated from mud sample was higher than that from water sample.

Conclusion: The genetic diversity of moderate halophilic bacteria isolated from Qrhan Salt Lake was abundant. Also, there were dominant and novel species of culturable moderate halophilic bacteria in this lake.

Objective: The present study aims to analyze the chemotaxis genes and proteins of several PAH-degrading Novosphingobium strains, and the chemotaxis of these strains toward aromatic compounds and intermediates.

Methods: Based on genome comparative analysis, we identified the chemotaxis genes organization and proteins distribution. We used drop and swarm plate assays to detect the chemotaxis of these strains toward aromatic compounds and intermediates of TCA cycle.

Results: We found that all these Novosphingobium strains showed chemotaxis, but the chemotatic ability varied. The completed genome sequenced strains N. pentaromativorans F2, N. pentaromativorans US6-1, N. pentaromativorans PP1Y, Novosphingobium sp. AP12, Novosphingobium sp. Rr 2-17, and Novosphingobium nitrogenifigens DSM 19370 contained MCP, CheW, CheA, CheB, CheR and CheY. Strain F2, US6-1 and PP1Y, shared a consistent order of chemotaxis genes in "che" cluster. The chemotatic system of these Novosphingobium strains belonged to the Fla chemotactic system.

Conclusion: These strains all contained a complete chmotaxis pathway. Their chemotactic ability toward aromatic compounds and intermediates varied, and the chemotaxis of US6-1 was obvious.

Quorum-sensing (QS) involved in the production of N-Acylhomoserine lactones (AHLs) is a universal way of communication of gram-negative bacteria. Complete AHL-QS system includes pairs of AHLs synthase belonging to LuxI family and cognate LuxR-family AHLs sensor-regulator. However, many gram-negative bacteria have evidenced the presence of AHL-QS related LuxR-type genes, which are unpaired to a cognate LuxI. These unpaired LuxRs have been called solos or orphans. LuxR solos are thought to be important for bacterial signal perception in eavesdropping, intra-species and inter-kingdom communication, which become research topic in the field of QS. Here, the finding, concept, protein structure, and main types of LuxR solos are illustrated. Furthermore, the function and important protein of LuxR solos associated with sensing AHLs or non-AHLs are reviewed. The prospect and significance of quorum sensing LuxR solos in bacteria are also discussed.

Objective: Endophytes are widespread in plants and build long-term mutually beneficial symbiotic relationship with the host. However, the mechanism of their interactions with the host needs further study. To explore the mechanism of endophytic bacterium ginkgo endophyte KM-1-2, we managed to forecast its secretory proteins based on its genome and explicit characteristics.

Methods: Signal peptide analysis software SignalP, transmembrane helical structure analysis software TMHMM and Phobius, cells position software PSORT, subcellar localization software TargetP and GPI anchor site analysis software big-PI Predictor were used to predict the scope of all secreted proteins, which were defined as secretome.

Results: Altogether 128 typical signal peptide secretory proteins were screened out of 5299 protein sequences in KM-1-2 genome, accounting for 2.4% of the whole genome. The shortest ORF encoding these proteins is 61 bp, the longest one is 2105 bp and the average is 373 bp. The length of the signal peptide guiding secretory protein was distributed between 15 to 37 aa, with the average length of 24 aa. Amino acid with the highest present frequency of signal peptide in proper order is alanine, leucine and valine. The type of signal peptide cleavage belongs to A-X-A which named SPI cleavage type. Among the total secretory proteins 66 pieces have functional description and 26 pieces were enzymes. These enzymes mainly include glycoside hydrolase, esterase transferase, REDOX enzyme and carbon oxygen lyase.

Conclusion: The predicted secretory proteins of Streptomyces lavendulae KM-1-2 were achieved through bioinformatics analysis. These secretory proteins involved some enzymes and other unknown functions. This result laid the foundation for further study between endophyte and host.