Salmonella typhimurium, causing mouse typhoid, infects hosts such as macrophage cells, and proliferates in intracellular vacuoles causing infected cells to trigger numerous genes to respond against the infection. In this study, we tried to identify such genes in RAW264.7 cells by using the PCR screening method with degenerate primers. Fourteen genes were found to be differentially expressed after a 4 h infection in which the expression of 8 genes increased while expression of the others decreased. Most of the genes were involved in proinflammatory responses such as cytokines production and cell death. The mutation in msbB gene encoding the myristoyl transferase in lipid A of lipopolysaccharide (LPS) resulted in much lower toxicity to the inoculated animals. We compared the expression of the identified genes in wild-type and msbB-mutated S. typhimurium infections and found that Lyzs encoding lysozyme type M was differentially expressed. This gene is quite likely to be related to bacterial survival in the host cells.

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Aims:  To investigate roles of quorum‐sensing (QS) system in Acinetobacter sp. strain DR1 and rifampicin‐resistant variant (hereinafter DR1R). Methods and Results:  The DR1 strain generated three putative acyl homoserine lactones (AHLs), while the DR1R produced only one signal and QS signal production was abrogated in the aqsI (LuxI homolog) mutant. The hexadecane‐degradation and biofilm‐formation capabilities of DR1, DR1R, and aqsI mutants were compared, along with their proteomic data. Proteomics analysis revealed that the AHL lactonase responsible for degrading QS signal was highly upregulated in both DR1R and aqsI mutant, also showed that several proteins, including ppGpp synthase, histidine kinase sensors, might be under the control of QS signalling. Interestingly, biofilm‐formation and hexadecane‐biodegradation abilities were reduced more profoundly in the aqsI mutant. These altered phenotypes of the aqsI mutant were restored via the addition of free wild‐type cell supernatant and exogenous C12‐AHL. Conclusions:  The QS system in strain DR1 contributes to hexadecane degradation and biofilm formation. Significance and Impact of the Study:  This is the first report to demonstrate that a specific QS signal appears to be a critical factor for hexadecane degradation and biofilm formation in Acinetobacter sp. strain DR1.

Rifampicin, a bactericidal antibiotic drug, is routinely used to make an environmental recipient selective in laboratory-conjugation experiments. We noticed, inadvertently, that the rifampicin-resistant Acinetobacter sp. strain DR1, a recently discovered hexadecane-degrading environmental isolate, exhibited a substantial loss of quorum sensing signalling. The domesticated ampicillin-resistant strain, DR1, evidenced more dramatic phenotypic changes than were observed in the rifampicin-resistant cells: a complete loss of quorum sensing, a loss in swimming and swarming motilities, poor fimbrial expression, increased rigidity in membrane fatty acid composition and reduced hexadecane degradation capability. Interestingly, the motility of strain DR1 grown adjacent to a streptomycin-producing Streptomyces griceus was permanently abrogated, where this change was heritable and other phenotypic changes could not be detected. In this study, we have reported for the first time that the in situ acquisition of antibiotic resistance may reduce biological fitness, including losses in the production of quorum sensing signals, motility and substrate utilization, and each antibiotic is associated with different degrees of phenotypic and genetic alterations. Our data also suggested that the domestication of environmental isolates should be approached with caution, as there are phenotypic variations in antibiotic-resistant cells that might not be noticeable unless all possible phenotypic assays are conducted.

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A novel bacterial strain, designated PMB02T, was isolated from a leaf of the tree Platanus orientalis. Colonies grown on TYG agar plates were circular, pink-pigmented and slow-growing, being 0.2–1.5 mm in diameter after 3 days growth. The cells of strain PMB02T were Gram-negative, aerobic, motile rods that possessed oxidase and catalase activities and grew at 20–30 °C, pH 6–8 and in media containing less than 1 % NaCl. The major respiratory quinone was identified as Q-10. A phylogenetic analysis based on 16S rRNA gene sequence comparisons indicated that strain PMB02T was related to members of the genus Methylobacterium. A comparative 16S rRNA gene sequence-based phylogenetic analysis placed the strain in a clade with the species Methylobacterium aquaticum and Methylobacterium variabile, with which it showed sequence similarities of 97.7 and 97.4 %, respectively. The values for DNA–DNA hybridization between strain PMB02T and M. aquaticum CCM 7218T and M. variabile GR3T were less than 32 %. On the basis of the phenotypic characterization, the phylogenetic analysis and the DNA–DNA relatedness data, strain PMB02T is considered to represent a novel species of the genus Methylobacterium, for which the name Methylobacterium platani sp. nov. is proposed. The type strain is PMB02T (=KCTC 12901T=JCM 14648T).

We tested the hypothesis that during metabolism of naphthalene and other substrates by Pseudomonas sp. strain As1 oxidative stress arises and can be reduced by antioxidant enzymes. Our approach was to prepare plasmid constructs that conferred expression of two single antioxidant enzymes [Fpr (ferredoxin-NADP + reductase) and SOD (superoxide dismutase)] and the pair of enzymes SOD plus AhpC (alkyl hydroperoxide reductase). The fpr, sodA and ahpC genes were placed under the transcriptional control of both the constitutive lac promoter and their respective native promoters. Both HPLC and growth-rate analyses showed that naphthalene metabolism was enhanced in the recombinant strains. All antioxidant-overexpressing recombinant strains, with the exception of one with an upregulated sodA gene due to the lac promoter [strain As1(sodA)], exhibited resistance to the superoxide generating agent paraquat (PQ). The growth of strain As1(sodA) was inhibited by PQ, but this growth defect was rapidly overcome by the simultaneous overproduction of AhpC, which is a known hydrogen peroxide scavenger. After PQinduced oxidative damage of the [Fe-S] enzyme aconitase, recovery of enzyme activity was enhanced in the recombinant strains. Reporter strains to monitor oxidative stress in strain As1 were prepared by fusing gfp (encoding green fluorescent protein, GFP) to the fpr promoter. Growth on salicylate and naphthalene boosted the GFP fluorescent signal 21-and 14-fold, respectively. Using these same oxidative stress reporters, overexpression of fpr and sodA was found to considerably reduce PQ-induced stress. Taken together, these data demonstrate that the overproduction of Fpr or SodA contributes to oxidative tolerance during naphthalene degradation; however, elevated SOD activity may trigger the generation of excess hydrogen peroxide, resulting in cell death.

We aimed to determine whether mycoplasmas are present in Korean chronic gastritis, and to understand their roles in gastric cancer tumorigenesis, because mycoplasmas resemble Helicobacter pylori in terms of ammonia production and induction of inflammatory cytokines in immune and non-immune cells. The presence and identity of mycoplasmas were assessed by semi-nested PCR and sequencing, and the results were compared with pathologic data. Fifty-six samples collected from Korean chronic gastritis patients were used for this study. Twenty-three (41.1%) were positive for mycoplasmas. Eighteen sequenced samples contained a single human mycoplasma or two mycoplasmas, which were identified as Mycoplasma faucium ( astric cancer can be caused by chronic Helicobacter pylori infection, which induces inflammatory cytokines and oxidative stress, and results in the accumulation of genetic alterations leading to transformation. However, only a proportion of H. pylori-positive patients develop a tumor, and it has been shown that vac A and cag A of H. pylori and host factors, such as single nucleotide polymorphisms (SNPs) in the promoter region of interleukin-1β (IL-1β) and IL-1β receptor antagonist (IL-1β Ra), are not related to gastric tumorigenesis [1][2][3][4] ; it therefore remains worthwhile to investigate other risk factors.Mycoplasmas are the smallest self-replicating bacteria. Although mycoplasmas are generally commensal parasites in humans, some species are real pathogens and are capable of causing a wide variety of diseases.5) Mycoplasmas present in the human oropharynx include Mycoplasma orale, M. salivarium, M. faucium, which produce ammonia and cause tissue damage, 6, 7) and M. fermentans, which induces inflammatory cytokines from macrophages 8) and epithelial cells. 9) Among them, M. salivarium and M. orale are major mycoplasmas found in throat specimens of adults, but M. faucium is relatively rare. 6)The presence of mycoplasmas in gastritis and gastrointestinal tumors has been reported. [10][11][12] These reports provoked concern about the epidemiological role of mycoplasmas in gastric cancer, though the fact that the identified species was of porcine origin, M. hyorhinis, was unexpected.10-12) Pathobiological similarities between mycoplasmas and H. pylori, and questions on additional risk factors in the tumorigenesis of Korean gastric cancer encouraged us to further investigate the detection and identification of mycoplasmas in chronic gastritis. 2)In this study, we investigated whether human mycoplasmas are associated with chronic gastritis by means of semi-nested PCR and direct sequencing. The results were then compared with pathologic data. Here, we report that human mycoplasmas are present in a high proportion of chronic gastritis (41.1%) cases, and the mycoplasma profiles are different from those of the oropharynx. In addition, mycoplasma-infected chronic gastritis recruits significantly more neutrophils than uninfected chronic gastritis (P<0.05), with no significant differences in the load of H. pylori (P>0....