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Archives of Microbiology (v.195, #3)

Geodermatophilus saharensis sp. nov., isolated from sand of the Saharan desert in Chad by M. C. Montero-Calasanz; M. Göker; G. Pötter; M. Rohde; C. Spröer; P. Schumann; A. A. Gorbushina; H.-P. Klenk (pp. 153-159).

A novel Gram-positive, aerobic, actinobacterial strain, CF5/5, was isolated from soil in the Sahara desert, Chad. It grew best at 20–35 °C and at pH 6.0–8.0 and with 0–4 % (w/v) NaCl, forming black-colored colonies. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The DNA G + C content was 75.9 mol%. The peptidoglycan contained meso-diaminopimelic acid; galactose and xylose were detected as diagnostic sugars. The main phospholipids were diphosphatidylglycerol, phosphatidylcholine, and phosphatidylinositol; MK-9(H₄) was the dominant menaquinone. The major cellular fatty acids were: iso-C_16:0 and iso-C_15:0. The 16S rRNA gene showed 95.6–98.3 % sequence similarity with the other named members of the genus Geodermatophilus. Based on the polyphasic taxonomy data, the isolate is proposed to represent a novel species, Geodermatophilus saharensis with the type strain CF5/5^T = DSM 45423 = CCUG 62813 = MTCC 11416.

Keywords: Actinomycetes; Geodermatophilaceae ; Taxonomy; Sahara desert; Phenotype microarray

Effect of acidic condition on the metabolic regulation of Escherichia coli and its phoB mutant by Lolo Wal Marzan; Chowdhury Mohammad Monirul Hasan; Kazuyuki Shimizu (pp. 161-171).

Effect of acidic condition on the fermentation characteristics was investigated by the continuous culture of Escherichia coli. In accordance with down-regulation of crp gene transcript level as well as up-regulation of arcA, the expressions of the TCA cycle genes were down-regulated, which caused more acetate formation at acidic condition under aerobic condition. It was also shown that yfiD was up-regulated in accordance with up-regulation of fnr, and the respiratory pathway genes were up-regulated under acidic condition. The effect of phoB gene knockout on fermentation characteristics was also investigated. Under micro-aerobic condition, the fermentation pattern changed in such a way that formate and lactate were more produced at lower pH due to up-regulations of pflA, yfiD and ldhA genes, whereas ethanol was less produced as compared to the case at neutral pH. The overall regulation mechanism under acidic condition was clarified based on fermentation characteristics and gene transcript levels.

Keywords: Metabolic regulation at low pH; Glutamate decarboxylase; Acidic condition; phoB mutant

Antimicrobial peptide from spider venom inhibits Chlamydia trachomatis infection at an early stage by Vassili N. Lazarev; Marina M. Shkarupeta; Nadezhda F. Polina; Elena S. Kostrjukova; Alexander A. Vassilevski; Sergey A. Kozlov; Eugene V. Grishin; Vadim M. Govorun (pp. 173-179).

Antichlamydial activity of cyto-insectotoxin 1a (CIT 1a), representative of a unique class of antimicrobial peptides from the venom of the Central Asian spider Lachesana tarabaevi, was studied. A plasmid vector expressing the cit 1a gene controlled by a human cytomegalovirus tetracycline-dependent promoter was constructed. Impressive inhibition of Chlamydia trachomatis infection in HEK 293 cells transfected by the cit 1a-harboring vector was achieved. With the use of various schemes of cell infection and gene expression induction, it was shown for the first time that an antimicrobial peptide exerts its potent antichlamydial action at an early stage of the pathogen life cycle.

Keywords: Antibacterial therapy; Cyto-insectotoxin; Chlamydial infection; Chlamydia life cycle; Lachesana tarabaevi

“Curing” of plasmid DNA in acetogen using microwave or applying an electric pulse improves cell growth and metabolite production as compared to the plasmid-harboring strain by Vel Berzin; Michael Kiriukhin; Michael Tyurin (pp. 181-188).

Plasmid-free acetogen Clostridium sp. MT962 electrotransformed with a small cryptic plasmid pMT351 was used to develop time- and cost-effective methods for plasmid elimination. Elimination of pMT351 restored production of acetate and ethanol to the levels of the plasmid-free strain with no dry cell weight changes. Destabilizing cell membrane via microwave at 2.45 GHz, or exposure to a single 12 ms square electric pulse at 35 kV cm⁻¹, eliminated pMT351 in 42–47 % of cells. Plasmid elimination with a single square electric pulse required 10 versus 0.1 J needed to introduce the same 3,202-bp plasmid into the cells as calculated per cell sample of Clostridium sp. MT962. Microwave caused visible changes in repPCR pattern and increased ethanol production at the expense of acetate. This is the first report on microwave of microwave ovens, wireless routers, and mobile devices causing chromosomal DNA aberrations in microbes along with carbon flux change.

Keywords: Plasmid elimination; Microwave; Pulse; Acetogens; Continuous syngas fermentation

Pseudomonas fluorescens can induce and divert the human β-defensin-2 secretion in intestinal epithelial cells to enhance its virulence by Amar Madi; Ziad Alnabhani; Charlène Leneveu; Lily Mijouin; Marc Feuilloley; Nathalie Connil (pp. 189-195).

The effect of intestinal molecules produced by the host on the virulence of Pseudomonas fluorescens is poorly documented. In the present work, we evaluated the secretion of human β-defensin-2 (hBD-2) by enterocytes after infection with P. fluorescens (a species previously suggested to be involved in inflammatory bowel disease) and investigated the effect of this host-defense peptide on the bacterial virulence. The results showed that P. fluorescens can induce hBD-2 production in Caco-2/TC7 cells via P38 and ERK MAPK-dependent pathways. Surprisingly, the exposure of P. fluorescens to low doses of the antimicrobial peptide was found to enhance its cytotoxic and proinflammatory effects suggesting a potential feedback mechanism in the dialog between bacteria and the host.

Keywords: P. fluorescens ; Caco-2/TC7; hBD-2; NF-κB; MAPK; Virulence

Investigation of spore coat display of Bacillus subtilis β-galactosidase for developing of whole cell biocatalyst by Setareh Tavassoli; Krzysztof Hinc; Adam Iwanicki; Michal Obuchowski; Gholamreza Ahmadian (pp. 197-202).

The production of highly efficient, recyclable and cost-effective enzymes is one of the most important goals in industrial biotechnology. Bacterial spores are highly resistant to harsh environmental conditions, easy to produce and are suitable for manipulation of genetic materials. These features make them a very efficient tool for biotechnology. Here, we show the use bacterial spores for presentation of functional enzyme. Spore coat display was used to produce a biocatalyst, which expresses β-galactiosidase (LacA). This enzyme is commonly used to produce lactose-free milk for lactose intolerant individuals. The lacA gene from Bacillus subtilis strain 168 was expressed on the surface of B. subtilis RH101(ΔcotC) spores using CotC as protein carrier. Presence of LacA protein is verified by western blotting. Results of β-galactiosidase assay show that the expressed enzyme retained its activity in condition of freezing and drying, as well as after recovery from the reaction’s mixture.

Keywords: Bacillus subtilis ; Spore surface display; Biocatalyst; β-Galactosidase; Spore coat proteins

Virulence determinants and biofilm production among Trueperella pyogenes recovered from abscesses of captive forest musk deer by Kelei Zhao; Yongqiang Tian; Bisong Yue; Hongning Wang; Xiuyue Zhang (pp. 203-209).

Trueperella pyogenes (formerly Arcanobacterium) is commonly isolated from domesticated or wild ruminants as an opportunistic pathogen. To investigate the role of virulence determinants (VDs) and biofilm production in T. pyogenes isolates, a total of 36 T. pyogenes were collected from abscesses of forest musk deer in Miyaluo Farm (Sichuan Province, China). The prevalence of VDs and associations with clonal types, antibiotic resistance and biofilm production were analyzed by PCR and bioassay. Finally, T. pyogenes isolates were separated into three clonal types based on the DNA fingerprinting of BOX-PCR. Isolates with less VDs obtained from sick forest musk deer were mainly belonged to Type 1, and the isolates with robust VD repertoire obtained from dead forest musk deer were included in Type 3. Accordingly, resistant isolates exhibited significant lower virulence than susceptible ones. Majority of T. pyogenes isolates of this study were capable of producing a biofilm. However, no VDs presence and antibiotic resistance were statistically associated with biofilm production. In conclusion, the current study demonstrated that T. pyogenes was probably the primary pathogen of abscesses in the forest musk deer. Moreover, as an animal origin pathogen, the increasing resistance of T. pyogenes isolates could also associate with a decreased virulence.

Keywords: Trueperella pyogenes ; Clonal type; Virulence determinants; Resistance; Biofilm

The novel NhaE-type Na⁺/H⁺ antiporter of the pathogenic bacterium Neisseria meningitidis by Pedro M. F. Sousa; Marco A. M. Videira; Thomas Vorburger; Sara T. N. Silva; James W. Moir; Julia Steuber; Ana M. P. Melo (pp. 211-217).

Neisseria meningitidis is a pathogenic bacterium responsible for meningitis. The mechanisms underlying the control of Na⁺ transmembrane movement, presumably important to pathogenicity, have been barely addressed. To elucidate the function of the components of the Na⁺ transport system in N. meningitidis, an open reading frame from the genome of this bacterium displaying similarity with the NhaE type of Na⁺/H⁺ antiporters was expressed in Escherichia coli and characterized for sodium transport ability. The N. meningitidis antiporter (NmNhaE) was able to complement an E. coli strain devoid of Na⁺/H⁺ antiporters (KNabc) respecting the ability to grow in the presence of NaCl and LiCl. Ion transport assays in everted vesicles prepared from KNabc expressing NmNhaE from a plasmid confirmed its ability to translocate Na⁺ and Li⁺. Here is presented the characterization of the first NhaE from a pathogen, an important contribution to the comprehension of sodium ion metabolism in this kind of microorganisms.

Keywords: Neisseria meningitidis ; Sodium transport; Na⁺/H⁺ antiporter; NhaE; Bioenergetics; Pathogen

Aggregation of selected plant growth promoting Methylobacterium strains: role of cell surface components and hydrophobicity by Manoharan Melvin Joe; Venkatakrishnan Sivaraj Saravanan; Tongmin Sa (pp. 219-225).

The bacterial cell surface plays a major role in the bacterial aggregation that in turn plays a positive role in affecting the bacterial dispersion and survival in soil and their ability to adhere to plant surfaces. Plant growth–promoting Methylobacterium strains, Methylobacterium goesingense CBMB5, Methylobacterium sp. CBMB12, Methylobacterium oryzae CBMB20, Methylobacterium fujisawaense CBMB37, M. oryzae CBMB110 and Methylobacterium suomiense CBMB120 were evaluated for aggregation efficiency. Aggregation occurred in all test strains under high C/N growth conditions, and the strain CBMB12 showed the highest aggregation of 53.4 % at 72 h. Disaggregation compound treatment studies revealed the role of protein–protein interaction in Methylobacterium strains except CBMB110 and CBMB120 strains, where a possible carbohydrate–protein interaction is suspected. Surface layer protein extraction by LiCl followed by SDS-PAGE analysis showed the presence of proteins at molecular weights ranging from 41 to 49 kDa. Methylobacterium strains under aggregated conditions showed increased hydrophobicity compared to the cells under standard grown conditions. A relatively higher hydrophobicity of 50.1 % as evident by the adhesion with xylene was observed with strain CBMB12 under aggregated condition. This study reports the aggregation ability in plant growth–promoting Methylobacterium strains and the possible involvement of cellular components and hydrophobicity in this phenomenon.

Keywords: Aggregation; Adhesion; Hydrophobicity; Methylobacterium ; Surface layer proteins

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Archives of Microbiology (v.195, #3)