Bacterial tail-specific proteases (Tsps) have been attributed a wide variety of functions including intracellular virulence, cell wall morphology, proteolytic signal cascades and stress response. This study tested the hypothesis that Tsp has a key function for the transmissive form of Legionella pneumophila. A tsp mutant was generated in Legionella pneumophila 130b and the characteristics of this strain and the isogenic wild-type were examined using a range of growth and proteomic analyses. Recombinant Tsp protein was also produced and analyzed. The L. pneumophila tsp mutant showed no defect in growth on rich media or during thermo-osmotic stress conditions. In addition, no defects in cellular morphology were observed when the cells were examined using transmission electron microscopy. Purified recombinant Tsp was found to be an active protease with a narrow substrate range. Proteome analysis using iTRAQ (5% coverage of the proteome) found that, of those proteins detected, only 5 had different levels in the tsp mutant compared to the wild type. ACP (Acyl Carrier Protein), which has a key role for Legionella differentiation to the infectious form, was reduced in the tsp mutant; however, tsp− was able to infect and replicate inside macrophages to the same extent as the wild type. Combined, these data demonstrate that Tsp is a protease but is not essential for Legionella growth or cell infection. Thus, Tsp may have functional redundancy in Legionella.
A moderately halophilic bacterium, strain HNA-14T, was isolated from a saline-alkali soil sample collected in Shache County, Xinjiang Province. On the basis of the polyphasic taxonomic data, the isolate was considered to be a member of the genus Bacillus. The organism grew optimally at 30°C and pH 8.0. It was moderately halophilic and its optimum growth occurred at 5−10% NaCl. The diamino acid found in the cell-wall peptidoglycan was meso-diaminopimelic acid and the predominant menaquinone was MK-7. The major cellular fatty acids were anteiso-C15:0 and iso-C15:0 and the polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannosides and two unknown phospholipids. The G+C content of the genomic DNA was 48.6 mol%. Strain HNA-14T exhibited a low 16S rRNA gene sequence similarity of 96% with its nearest neighbors [Bacillus clausii KSM-K16 (96.5%), Bacillus xiaoxiensis DSM 21943T(96.2%), Bacillus clausii DSM 8716T (96.1%), Bacillus patagoniensis PAT05T (96.1%), Bacillus lehensis MLB-2T (96.0%), Bacillus oshimensis K11T (95.9%) and Bacillus hunanensis DSM 23008T (95.8%)] and the phenotypic characteristics indicate that strain HNA-14T can be distinguished from them. Therefore, a novel species of the genus Bacillus, Bacillus shacheensis sp. nov. (type strain, HNA-14T=KCTC 33145=DSM 26902) is proposed.
This paper is concerned with optimization of fermentation conditions for lipstatin production with Streptomyces toxytricini zjut011 by the single factor and orthogonal tests. Five single factors of important effects on lipstatin production were explored. L-Leucine was identified to be the most suitable precursor for lipstatin biosynthesis and for the first time the divalent cations Mg2+, Co2+ and Zn2+ were found to have significant effect on enhancing lipstatin fermentation titer. The effects of the additives on the lipstatin production were in the order of L-leucine ＞ Mg2+ ＞ Co2+ ＞ Zn2+ ＞ octanoic acid. The optimized conditions for lipstatin production were determined as 45.72 mmol/L of L-leucine (added on the 4 th day), 31.1985 mmol/L of octanoic acid (added on the 6th day), 12 mmol/L of Mg2+, 1 mmol/L of Co2+ and 0.25 mmol/L of Zn2+. Under these conditions, a maximum lipstatin of 4.208 g/ml was achieved in verification experiments in 500 ml shake flasks.
Some microorganisms, such as Escherichia coli, harbor transhydrogenases that catalyze the interconversion between NADPH and NADH. However, such transhydrogenase genes have not been found in the genome of a glutamic acid-producing bacterium Corynebacterium glutamicum. In this study, the E. coli transhydrogenase genes udhA and pntAB were introduced into the C. glutamicum wild-type strain ATCC 13032, and the metabolic characteristics of the recombinant strains under aerobic and microaerobic conditions were examined. No major metabolic changes were observed following the introduction of the E. coli transhydrogenase genes under aerobic conditions. Under microaerobic conditions, significant metabolic change was not observed following the introduction of the udhA gene. However, the specific production rates of lactic acid, acetic acid, and succinic acid, and the overall production levels of acetic acid and succinic acid were increased by introducing the E. coli pntAB gene. Moreover, the NADH/NAD+ ratio was increased by introduction of pntAB. Our results suggest that the E. coli PntAB transhydrogenase enhances the conversion of NADPH to NADH in C. glutamicum under microaerobic conditions, and the increased NADH/NAD+ ratio results in increased succinic acid production. In addition, acetic acid production might be enhanced to supply ATP to the anaplerotic reaction catalyzed by pyruvate carboxylase.