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Archives of Microbiology (v.195, #2)
Repression of oxalic acid-mediated mineral phosphate solubilization in rhizospheric isolates of Klebsiella pneumoniae by succinate by Mahendrapal Singh Rajput; G. Naresh Kumar; Shalini Rajkumar (pp. 81-88).
Two strains of Klebsiella (SM6 and SM11) were isolated from rhizospheric soil that solubilized mineral phosphate by secretion of oxalic acid from glucose. Activities of enzymes for periplasmic glucose oxidation (glucose dehydrogenase) and glyoxylate shunt (isocitrate lyase and glyoxylate oxidase) responsible for oxalic acid production were estimated. In presence of succinate, phosphate solubilization was completely inhibited, and the enzymes glucose dehydrogenase and glyoxylate oxidase were repressed. Significant activity of isocitrate lyase, the key enzyme for carbon flux through glyoxylate shunt and oxalic acid production during growth on glucose suggested that it could be inducible in nature, and its inhibition by succinate appeared to be similar to catabolite repression.
Keywords: Klebsiella ; Mineral phosphate solubilization; Oxalic acid; Glyoxylate shunt; Catabolite repression
Protozoa and human macrophages infection by Legionella pneumophila environmental strains belonging to different serogroups by Messi Patrizia; Bargellini Annalisa; Anacarso Immacolata; Marchesi Isabella; Simona de Niederhäusern; Bondi Moreno (pp. 89-96).
Three Legionella pneumophila strains isolated from municipal hot tap water during a multicentric Italian survey and belonging to serogroups 1, 6, 9 and the reference strain Philadelphia-1 were studied to determine the intracellular replication capability and the cytopathogenicity in human monocyte cell line U937 and in an Acanthamoeba polyphaga strain. Our results show that both serogroups 1 and Philadelphia-1 were able to multiply into macrophages inducing cytopathogenicity, while serogroup 6 and ever more serogroup 9 were less efficient in leading to death of the infected macrophages. Both serogroups 1 and 6 displayed a quite good capability of intracellular replication in A. polyphaga, although serogroup 1 was less cytopathogenic than serogroup 6. Serogroup 9, like Philadelphia-1 strain, showed a reduced efficiency of infection and replication and a low cytopathogenicity towards the protozoan. Our study suggests that bacterial pathogenesis is linked to the difference in the virulence expression of L. pneumophila serogroups in both hosts, as demonstrated by the fact that only L. pneumophila serogroup 1 shows the contextual expression of the two virulence traits. Serogroup 6 proves to be a good candidate as pathogen since it shows a good capacity for intracellular replication in protozoan.
Keywords: Legionella pneumophila ; Serogroups; U937 macrophages; Acanthamoeba polyphaga
Erratum to: Protozoa and human macrophages infection by Legionella pneumophila environmental strains belonging to different serogroups
by Patrizia Messi; Annalisa Bargellini; Immacolata Anacarso; Isabella Marchesi; Simona de Niederhäusern; Moreno Bondi (pp. 97-97).
Filamentous fungi from the Atlantic marine sponge Dragmacidon reticulatum by Michel R. Z. Passarini; Cledir Santos; Nelson Lima; Roberto G. S. Berlinck; Lara D. Sette (pp. 99-111).
Dragmacidon reticulatum is a marine sponge of wide occurrence in the Eastern and Western Atlantic. Little is known about D. reticulatum fungal diversity. Filamentous fungi recovered from D. reticulatum were assessed in the present study using a polyphasic taxonomic approach, including classical morphology, molecular biology and MALDI-TOF ICMS. Ninety-eight fungal strains were isolated from two D. reticulatum samples by using six different culture media, which were identified up to the genus level. Sixty-four distinct fungal ribotypes were obtained, distributed among twenty-four different genera belonging to the Ascomycota and Zygomycota. Representatives of Penicillium and Trichoderma were the most diverse and abundant fungi isolated. Amongst Penicillium spp. three isolates belonged to the same ribotype can be considered as a putative new species. Data derived from the present study highlight the importance of using a polyphasic approach to get an accurate identification in order to structure a reliable culture collection.
Keywords: Filamentous fungi; MALDI-TOF ICMS; Marine sponge; Polyphasic taxonomy
RsbV of Listeria monocytogenes contributes to regulation of environmental stress and virulence by Zaichao Zhang; Qingling Meng; Jun Qiao; Lihong Yang; Xuepeng Cai; Guanglei Wang; Chuangfu Chen; Lijuan Zhang (pp. 113-120).
SigmaB factor is an important regulatory factor for stress response in Gram-positive bacteria such as Listeria monocytogenes (L. monocytogenes), Staphylococcus aureus and Bacillus subtilis. However, the activity of SigmaB factor is regulated by RsbV factor. Currently, the functional studies of RsbV factor are mostly focused on non-pathogenic B. subtilis, but the roles of RsbV factor in pathogenic L. monocytogenes during the regulation of environmental stress and virulence are still unclear. In the study, a ∆RsbV mutant of L. monocytogenes was constructed to explore the regulatory role of RsbV in environmental stress and virulence. The environmental stress experiments indicated that the growth and survival capability of ∆RsbV mutant obviously decreased in stress of low temperature, osmotic pressure, alcohol and acid, compared with EGD strain. The macrophage infection experiment indicated that ∆RsbV mutant had weaker survival capability than EGD strain, and the expression of PrfA, actA, PlcA and LLO was down-regulated in infected cells. Animal inoculation experiments indicated that RsbV deletion significantly reduced the pathogenicity of L. monocytogenes. Our data demonstrate that, in addition to regulating tolerance under environmental stress conditions, RsbV also contributes to regulation of L. monocytogenes virulence.
Keywords: Listeria monocytogenes ; RsbV; Stress tolerance; Virulence
Identification of fitness determinants in Enterococcus faecalis by differential proteomics by Angela G. Lindenstrauß; Jürgen Behr; Matthias A. Ehrmann; Dirk Haller; Rudi F. Vogel (pp. 121-130).
Enterococcus (E.) faecalis is found as commensal in healthy humans, in a variety of fermented foods. It can serve as probiotic but also as pathogen causing endocarditis, bacteremia and urinary tract infections. We have employed a proteomic study with E. faecalis strain OG1RF under different growth conditions and in contact to mouse intestinal cells to identify novel latent and adaptive fitness determinants. These relate to changes in catabolic pathways (BudA), protein biosynthesis (AsnS), cellular surface biosynthesis (RmlA) and regulatory mechanisms (OmpR). This knowledge can be used to derive novel evidence-based targets, which can be used to further elucidate gene expression changes enhancing pathogenicity or fitness in a commensal strain and possibly delineate this species into groups of higher and lower risk for applications in a food or a medical context versus improved treatment strategies of the so far hard to cure diseases.
Keywords: Enterococcus faecalis ; 2D Gel electrophoresis
Polyvinyl alcohol and polyethylene glycol form polymer bodies in the periplasm of Sphingomonads that are able to assimilate them by Fusako Kawai; Sakihito Kitajima; Kenji Oda; Takahiko Higasa; Jittima Charoenpanich; Xiaoping Hu; Rie Mamoto (pp. 131-140).
Scanning electron microscopy (SEM) shows remarkable morphological surface changes in Sphingopyxis sp. 113P3 cells grown in polyvinyl alcohol (PVA) but not in Luria–Bertani medium (LB) (Hu et al. in Arch Microbiol 188: 235–241, 2007). However, transmission electron microscopy showed no surface changes in PVA-grown cells and revealed the presence of polymer bodies in the periplasm of PVA-grown cells, which were not observed in LB-grown cells. The presence of polymer bodies was supported by low-vacuum SEM observation of PVA- and LB-grown cells of strain 113P3, and the presence of similar polymer bodies was also found when Sphingopyxis macrogoltabida 103 and S. terrae were grown in polyethylene glycol (PEG). The extraction of PVA and PEG from the periplasmic fraction of cells using a modified Anraku and Heppel method and their analysis by MALDI–TOF mass spectrometry strongly suggested that the polymer bodies are composed of PVA and PEG, respectively, in Sphingopyxis sp. 113P3 (PVA degrader) and Sphingopyxis macrogoltabida 103 or S. terrae (PEG degraders). PEG-grown S. macrogoltabida 103 and S. terrae showed higher transport of 14C-PEG 4000 than LB-grown cells. Recombinant PegB (TonB-dependent receptor-like protein consisting of a barrel structure) interacted with PEG 200, 4000 and 20000, suggesting that the barrel protein in the outer membrane contributes to the transport of PEG into the periplasm.
Keywords: Sphingopyxis sp. 113P3; Sphingopyxis macrogoltabida 103; S. terrae ; Polymer bodies; PVA and PEG uptake
Molecular characterization of extended-spectrum-beta-lactamase-producing Escherichia coli isolates from red foxes in Portugal by Hajer Radhouani; Gilberto Igrejas; Alexandre Gonçalves; Vanesa Estepa; Roberto Sargo; Carmen Torres; Patrícia Poeta (pp. 141-144).
The presence of broad-spectrum-cephalosporin-resistant Escherichia coli isolates and the implicated mechanisms of resistance and virulence factor genes were investigated in red fox (Vulpes vulpes) in Portugal. Cefotaxime-resistant E. coli isolates were isolated from two of 52 fecal samples (4 %), being both ESBL producers. The β-lactamase genes found in the two isolates were bla SHV-12 + bla TEM-1b. The tet(A) and sul2 genes were also detected in these isolates, together with the non-classical class 1 integron (intI1-dfrA12-orfF-aadA2-cmlA1-aadA1-qacH-IS440-sul3) with the PcH1 promoter. The two isolates belonged to the phylogroup A. Amino acid changes in GyrA (S83L + D87G) and ParC (S80I) proteins were identified in our study. Concerning MLST typing, both isolates were assigned to ST1086, never found before in wild animals, and they presented closely related PFGE patterns. This study reveals the presence of ESBL-producing E. coli isolates, in a wild ecosystem, which could be disseminated through the environment to other niches.
Keywords: ESBLs; Escherichia coli ; Phylogenetic groups; Vulpes vulpes ; Virulence factors
Natronorubrum texcoconense sp. nov., a haloalkaliphilic archaeon isolated from soil of the former lake Texcoco (Mexico) by Erick Ruiz-Romero; César Valenzuela-Encinas; María Patricia López-Ramírez; María de los Angeles Coutiño-Coutiño; Rodolfo Marsch; Luc Dendooven (pp. 145-151).
A new haloalkaliphilic archaeon, strain B4T, was isolated from the former lake Texcoco in Mexico. The cells were Gram-negative, pleomorphic-shaped, pink to red pigmented and aerobic. Strain B4T required at least 2.5 M NaCl for growth, with optimum growth at 3.4 M NaCl. It was able to grow over a pH range of 7.5–10.0 and temperature of 25–50 °C, with optimal growth at pH 9 and 37 °C. Cells are lysed in hypotonic treatment with less than 1.3 M NaCl. The major polar lipids of strain B4T were phosphatidylglycerol and methyl-phosphatidylglycerophosphate. Phospholipids were detected, but not glycolipids. The nucleotide sequence of the 16S rRNA gene revealed that the strain B4T was phylogenetically related to members of the genus Natronorubrum. Sequence similarity with Natronorubrum tibetense was 96.28 %, with Natronorubrum sulfidifaciens 95.06 % and Natronorubrum sediminis 94.98 %. The G+C content of the DNA was 63.3 mol%. The name of Natronorubrum texcoconense sp. nov. is proposed. The type strain is B4T (=CECT 8067T = JCM 17497T).
Keywords: Halobacteriaceae ; Natronorubrum ; Archaea; Soil of the former lake Texcoco; 16S rRNA gene