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Archives of Microbiology (v.195, #1)

Pannonibacter indica sp. nov., a highly arsenate-tolerant bacterium isolated from a hot spring in India by Saumya Bandyopadhyay; Peter Schumann; Subrata K. Das (pp. 1-8).

A novel aerobic bacterium, strain HT23^T, able to grow on 500 mM sodium arsenate was isolated from a hot-spring sediment sample collected from Athamallik, Orissa, India. Cells of this isolate were Gram negative. Heterotrophic growth was observed at pH 6.0–11.0 and 20–45 °C. Optimum growth was observed at 37 °C and pH 7.0–10.0. The major polar lipids are diphosphatidyl glycerol, phosphatidyl glycerol, phosphatidyl ethanolamine, phosphatidyl choline and phosphatidyl monomethyl ethanolamine. The major isoprenoid quinone was Q-10. 16S rRNA gene sequence analysis indicated that the bacterium clustered with the genus Pannonibacter and showed 98.9 % similarity with Pannonibacter phragmitetus C6-19^T (DSM 14782^T) and 98 % with the P. phragmitetus group B and P. phragmitetus group E strains. Levels of DNA–DNA relatedness between the strain HT23^T and P. phragmitetus C6-19^T (DSM 14782^T) and other strains of P. phragmitetus group B and group E strains were below 55 %. On the basis of phenotypic and chemotaxonomic characteristics, 16S rRNA gene sequence analysis and DNA–DNA hybridization data, strain HT23^T is considered to represent a novel species of the genus Pannonibacter, for which the name Pannonibacter indica sp. nov. is proposed. The type strain is HT23^T (=JCM 16851^T = DSM 23407^T = LMG 25769^T).

Keywords: Class Alphaproteobacteria; Pannonibacter indica sp. nov; Phenotype; Phylogeny; Arsenate resistance; Hot-spring sediments

Is l-arabinose important for the endophytic lifestyle of Pseudomonas spp.? by Natalia Malfanova; Faina Kamilova; Shamil Validov; Vladimir Chebotar; Ben Lugtenberg (pp. 9-17).

Twenty endophytic bacteria were isolated from surface-sterilized stems and roots of cucumber plants. After removal of potential siblings and human pathogens, the remaining seven strains were identified based on their 16S rDNA as Pseudomonas fluorescens (2 strains) and P. putida (5 strains). Three strains, namely P. fluorescens CS1, P. fluorescens CR2 and P. putida CR3, were able to suppress tomato foot and root rot (TFRR). Special attention was paid to the characterization of the BIOLOG carbon oxidation profiles of the isolated pseudomonads in order to identify nutrients which might be important for their endophytic lifestyle. Comparative analysis of the profiles of these seven strains with those of seven rhizospheric Pseudomonas spp. revealed that endophytes were able to oxidize l-arabinose and 2,3-butanediol significantly more often than the rhizospheric group. An independent growth experiment performed in tubes using l-arabinose and 2,3-butanediol as sole carbon sources showed the same results as seen using BIOLOG for l-arabinose, but not for 2,3-butanediol. Since l-arabinose is one of the most abundant sugars in xylem of cucumber plants and was not detected in their rhizosphere, our data suggest that utilization of l-arabinose might be a trait contributing to the endophytic lifestyle of the isolated Pseudomonas endophytes.

Keywords: Endophytic; Pseudomonas ; Biocontrol; BIOLOG

Influence of planktonic and sessile Listeria monocytogenes on Caenorhabditis elegans by Sujay Guha; Miranda Klees; Xiaoxia Wang; Jing Li; Yuqing Dong; Min Cao (pp. 19-26).

Listeria monocytogenes is the etiologic agent of listeriosis, a food-borne disease affecting humans and a variety of animals. In order to combat this pathogen, it is crucial to have an understanding of its natural interplay with the environment. For this reason, the free soil nematode Caenorhabditis elegans was focused upon because of its shared natural habitat with Listeria and its potential as a model organism for Listeria pathogenesis. Previous studies have generated some contradictory results on Listeria’s ability to kill C. elegans, making additional interaction studies such as this more attractive. In our study, we carried out a series of killing assays in a systematic manner using different Listeria strains under different growth conditions. In addition to studying the effects of planktonic cells, we examined the interaction between C. elegans and sessile listerial cells. Our findings suggest that, rather than causing infection and death, L. monocytogenes may extend the life span of C. elegans. This indicates that Listeria is not pathogenic to C. elegans. We also found that C. elegans can feed and ingest sessile cells, as well as carry the pathogen in its gut, implying that C. elegans could be a vehicle for L. monocytogenes spread in the environment.

Keywords: Listeria monocytogenes ; PrfA; Caenorhabditis elegans ; Life span; Mutualism; Model system

Phenotypic analysis of Salmonella enterica serovar Typhimurium rpoE mutants encoding RNA polymerase extracytoplasmic stress response sigma factors σ^E with altered promoter specificity by Bronislava Rezuchova; Dagmar Homerova; Beatrica Sevcikova; Renata Novakova; Lubomira Feckova; Mark Roberts; Jan Kormanec (pp. 27-36).

We previously identified mutants in the rpoE gene of Salmonella enterica serovar Typhimurium (S. Typhimurium) encoding RNA polymerase extracytoplasmic stress response sigma factors σ^E with altered promoter specificity. The replacement of the conserved R171 residue in the conserved region 4.2 of σ^E by different amino acid residues exhibited different phenotypes. While R171A almost completely abolished sigma factor activity, R171G and R171C mutant changes imparted a relaxed recognition phenotype to the sigma factor. In the present study, we introduced these mutations into the S. Typhimurium chromosome to investigate their phenotype during ethanol stress and in promoter recognition. Both relaxed sigma factors were found to initiate transcription from a high number of artificial promoters in the S. Typhimurium genome. Both mutants had substantially decreased activity under stress conditions. However, this decreased activity and also the recognition of atypical promoters had no significant effect upon growth, even in stressful conditions.

Keywords: Envelope stress response; Salmonella enterica serovar Typhimurium; Sigma factor; S1 mapping analysis; Expression

PFGE and AFLP genotyping of Staphylococcus aureus subsp. anaerobius isolated from goats with Morel’s disease by O. Szaluś-Jordanow; D. Chrobak; M. Pyrgiel; A. Lutyńska; J. Kaba; M. Czopowicz; L. Witkowski; M. Kizerwetter-Świda; M. Binek; T. Frymus (pp. 37-41).

Staphylococcus aureus subsp. anaerobius is the etiological agent of the Morel’s disease in sheep and goats. The disease presents with subcutaneous abscesses, located mainly in the superficial lymph nodes. Forty-one isolates of S. aureus subsp. anaerobius were collected from two outbreaks of the Morel’s disease in Poland in years 2006–2008. Analysis of DNA SmaI digests by PFGE showed that 35 of 41 isolates belonged to the same PFGE type, identical to the type strain of S. aureus subsp. anaerobius ATCC 35844, confirming high level of clonality of the species. The DNA patterns of the remaining identical 6 isolates, different from the reference strain only by two bands, were found closely related. Genotyping performed with AFLP technique revealed two clonal groups including 16 and 25 isolates, respectively. The study indicated that AFLP technique might be a better discriminatory tool for genetic analysis of S. aureus subsp. anaerobius isolates, when compared to PFGE.

Keywords: PFGE; AFLP; Staphylococcus aureus subsp. anaerobius ; Goat; Morel’s disease

Streptococcus danieliae sp. nov., a novel bacterium isolated from the caecum of a mouse by Thomas Clavel; Cédric Charrier; Dirk Haller (pp. 43-49).

We report the characterization of one novel bacterium, strain ERD01G^T, isolated from the cecum of a TNF^deltaARE mouse. The strain was found to belong to the genus Streptococcus based on phylogenetic analysis of partial 16S rRNA gene sequences. The bacterial species with standing name in nomenclature that was most closely related to our isolate was Streptococcus alactolyticus (97 %). The two bacteria were characterized by a DNA–DNA hybridization similarity value of 35 %, demonstrating that they belong to different species. The new isolate was negative for acetoin production, esculin hydrolysis, urease, α-galactosidase and β-glucosidase, was able to produce acid from starch and trehalose, grew as beta-hemolytic coccobacilli on blood agar, did not grow at >40 °C, did not survive heat treatment at 60 °C for 20 min and showed negative agglutination in Lancefield tests. On the basis of these characteristics, strain ERD01G^T differed from the most closely related species S. alactolyticus, Streptococcus gordonii, Streptococcus intermedius and Streptococcus sanguinis. Thus, based on genotypic and phenotypic evidence, we propose that the isolate belongs to a novel bacterial taxon within the genus Streptococcus, for which the name Streptococcus danieliae is proposed. The type strain is ERD01G^T (= DSM 22233^T = CCUG 57647^T).

Keywords: TNF^deltaARE mice; Crohn’s disease-like ileitis; Intestinal microbiota; Bacterial culture; Streptococcus

The mitochondrial respiratory chain of Rhizopus stolonifer (Ehrenb.:Fr.) Vuill by Leobarda Robles-Martínez; María Guadalupe Guerra-Sánchez; Oscar Flores-Herrera; Ana Niurka Hernández-Lauzardo; Miguel Gerardo Velázquez-Del Valle; Juan Pablo Pardo (pp. 51-61).

Rhizopus stolonifer (Ehrenb.:Fr.) Vuill mitochondria contain the complete system for oxidative phosphorylation, formed by the classical components of the electron transport chain (complexes I, II, III, and IV) and the F₁F₀-ATP synthase (complex V). Using the native gel electrophoresis, we have shown the existence of supramolecular associations of the respiratory complexes. The composition and stoichiometry of the oxidative phosphorylation complexes were similar to those found in other organisms. Additionally, two alternative routes for the oxidation of cytosolic NADH were identified: the alternative NADH dehydrogenase and the glycerol-3-phosphate shuttles. Residual respiratory activity after inhibition of complex IV by cyanide was inhibited by low concentrations of n-octyl gallate, indicating the presence of an alternative oxidase. The K_0.5 for the respiratory substrates NADH, succinate, and glycerol-3-phosphate in permeabilized cells was higher than in isolated mitochondria, suggesting that interactions of mitochondria with other cellular elements might be important for the function of this organelle.

Keywords: Oxidative phosphorylation; F₁F₀-ATP synthase; Respiratory supercomplexes; NADH dehydrogenase; Glycerol-3-phosphate shuttle

Wavelength dependence of biological damage induced by UV radiation on bacteria by Ana L. Santos; Vanessa Oliveira; Inês Baptista; Isabel Henriques; Newton C. M. Gomes; Adelaide Almeida; António Correia; Ângela Cunha (pp. 63-74).

The biological effects of UV radiation of different wavelengths (UVA, UVB and UVC) were assessed in nine bacterial isolates displaying different UV sensitivities. Biological effects (survival and activity) and molecular markers of oxidative stress [DNA strand breakage (DSB), generation of reactive oxygen species (ROS), oxidative damage to proteins and lipids, and the activity of antioxidant enzymes catalase and superoxide dismutase] were quantified and statistically analyzed in order to identify the major determinants of cell inactivation under the different spectral regions. Survival and activity followed a clear wavelength dependence, being highest under UVA and lowest under UVC. The generation of ROS, as well as protein and lipid oxidation, followed the same pattern. DNA damage (DSB) showed the inverse trend. Multiple stepwise regression analysis revealed that survival under UVA, UVB and UVC wavelengths was best explained by DSB, oxidative damage to lipids, and intracellular ROS levels, respectively.

Keywords: UV radiation; Bacteria; Inactivation; Oxidative stress

PknE, a serine/threonine protein kinase from Mycobacterium tuberculosis has a role in adaptive responses by Dinesh Kumar; Kannan Palaniyandi; Vijay K. Challu; Prahlad Kumar; Sujatha Narayanan (pp. 75-80).

Serine/threonine protein kinases (STPK) play a major role in the physiology and pathogenesis of Mycobacterium tuberculosis. Here, we have examined the role of pknE, a STPK in the adaptive responses of M. tuberculosis using a deletion mutant ΔpknE. The survival of ΔpknE was assessed in the presence of stress (pH, surfactant and cell wall–damaging agents) and anti-tuberculosis drugs. ΔpknE had a defective growth in pH 7.0 and lysozyme (a cell wall–damaging agent) with better survival in pH 5.5, SDS and kanamycin (a second-line anti-tuberculosis drug). Furthermore, ΔpknE was reduced in cell size during growth in liquid media and exhibited hypervirulence in a guinea pig model of infection. In conclusion, our data suggest that pknE plays a role in adaptive response of M. tuberculosis regulating cellular integrity and survival.

Keywords: Mycobacterium tuberculosis ; STPK; PknE and stress

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Archives of Microbiology (v.195, #1)

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Archives of Microbiology (v.195, #1)