Microbiology Medical and Health News Headlines

Poor Sensitivity of the Signify H. pylori Test.

Curr Microbiol. 2008 Oct 2;

Authors: Chong VH

PMID: 18830744 [PubMed - as supplied by publisher]

Presence of pRI1: A Small Cryptic Mobilizable Plasmid Isolated from Enterococcus faecium of Human and Animal Origin.

Curr Microbiol. 2008 Oct 2;

Authors: Garcia-Migura L, Hasman H, Jensen LB

This study focused on the molecular characterization of a small cryptic, mobilizable plasmid (6038 bp) sequenced from an E. faecium 9631160-1 of poultry origin. Sequence analysis of pRI1 revealed seven open reading frames. pRI1 contained an IS 100% identical to ISEfa4. This insertion element disrupted a putative mobilization gene (mobA) which presented 99% similarity to the one described in plasmid pJS42 (NC_010291). pRI1 harbored a cluster of four coding sequences which exhibited a homology to those described in contig 658 (from nucleotide 8940 to nt 10515) of E. faecium DO. In addition, a rep almost identical to the repA from the pEFNP1 and pKQ10 plasmids from E. faecium was also identified. Presence of the pRI1 replication initiation gene (rep) was analyzed in a panel of 159 E. faecium isolates of human and animal origin from different European countries, of which 60 tested positive for the presence of pRI1-rep. Conjugation experiments verified transfer of the pRI1 together with conjugative plasmids harboring resistance to vancomycin and streptogramin. The presence of pRI1 in enterococcal isolates geographically separated and from different origin demonstrates the ability of enterococci to acquire and transfer mobile genetic elements, emphasizing the need for further studies to reveal the meaning and role that these cryptic plasmids play in nature.

PMID: 18830745 [PubMed - as supplied by publisher]

Four novel Candida species in the Candida albicans/Lodderomyces elongisporus clade isolated from the gut of flower beetles.

Antonie Van Leeuwenhoek. 2008 Oct 2;

Authors: Ji ZH, Jia JH, Bai FY

Flower-visiting beetles belonging to three species of Cetoniidae were collected on three mountains near Beijing, China, and yeasts were isolated from the gut of the insects collected. Based on the 26S rDNA D1/D2 domain and internal transcribed spacer (ITS) region sequence analysis and phenotypic characterization, four novel anamorphic yeast species located in the Candida albicans/Lodderomyces elongisporus clade were identified from 18 of the strains isolated. The new species and type strains are designated as Candida blackwellae AS 2.3639(T) (=CBS 10843(T)), Candida jiufengensis AS 2.3688(T) (=CBS 10846(T)), Candida oxycetoniae AS 2.3656(T) (=CBS 10844(T)), and Candida pseudojiufengensis AS 2.3693(T) (=CBS 10847(T)). C. blackwellae sp. nov. was basal to the branch formed by C. albicans and C. dubliniensis with moderately strong bootstrap support. The closest relative of C. oxycetoniae was L. elongisporus. C. jiufengensis sp. nov. and C. pseudojiufengensis sp. nov. were closely related with each other and formed a branch in a subclade represented by C. parapsilosis and L. elongisporus.

PMID: 18830804 [PubMed - as supplied by publisher]

Characterization of extracellular esterase and lipase activities from five halophilic archaeal strains.

J Ind Microbiol Biotechnol. 2008 Oct 2;

Authors: Ozcan B, Ozyilmaz G, Cokmus C, Caliskan M

A total of 118 halophilic archaeal collection of strains were screened for lipolytic activity and 18 of them were found positive on Rhodamine agar plates. The selected five isolates were further characterized to determine their optimum esterase and lipase activities at various ranges of salt, temperature and pH. The esterase and lipase activities were determined by the hydrolysis of pNPB and pNPP, respectively. The maximum hydrolytic activities were found in the supernatants of the isolates grown at complex medium with 25% NaCl and 1% gum Arabic. The highest esterase activity was obtained at pH 8-8.5, temperature 60-65 degrees C and NaCl 3-4.5 M. The same parameters for the highest lipase activities were found to be pH 8, temperature 45-65 degrees C and NaCl 3.5-4 M. These results indicate the presence of salt-dependent and temperature-tolerant lipolytic enzymes from halophilic archaeal strains. Kinetic parameters were determined according to Lineweaver-Burk plot. The KM and V (max) values were lower for pNPP hydrolysis than those for pNPB hydrolysis. The results point that the isolates have higher esterase activity comparing to lipase activity.

PMID: 18830729 [PubMed - as supplied by publisher]

The behavior of key enzymes of xylose metabolism on the xylitol production by Candida guilliermondii grown in hemicellulosic hydrolysate.

J Ind Microbiol Biotechnol. 2008 Oct 2;

Authors: Gurpilhares DB, Hasmann FA, Pessoa A, Roberto IC

A variety of raw materials have been used in fermentation process. This study shows the use of rice straw hemicellulosic hydrolysate, as the only source of nutrient, to produce high added-value products. In the present work, the activity of the enzymes xylose reductase (XR); xylitol dehydrogenase (XD); and glucose-6-phosphate dehydrogenase (G6PD) during cultivation of Candida guilliermondii on rice straw hemicellulosic hydrolysate was measured and correlated with xylitol production under different pH values (around 4.5 and 7.5) and initial xylose concentration (around 30 and 70 g l(-1)). Independent of the pH value and xylose concentration evaluated, the title of XD remained constant. On the other hand, the volumetric activity of G6PD increased whereas the level of XR decreased when the initial xylose concentration was increased from 30 to 70 g l(-1). The highest values of xylitol productivity (Q (P) approximately 0.40 g l(-1)) and yield factor (Y (P/S) approximately 0.60 g g(-1)) were reached at highest G6PD/XR ratio and lowest XR/XD ratio. These results suggest that NADPH concentrations influence the formation of xylitol more than the activity ratios of the enzymes XR and XD. Thus, an optimal rate between G6PD and XR must be reached in order to optimize the xylitol production.

PMID: 18830730 [PubMed - as supplied by publisher]

The chronicles of Porphyromonas gingivalis: the microbium, the human oral epithelium and their interplay.

Microbiology. 2008 Oct;154(Pt 10):2897-903

Authors: Yilmaz O

The microbiota of the human oral mucosa consists of a myriad of bacterial species that normally exist in commensal harmony with the host. Porphyromonas gingivalis, an aetiological agent in severe forms of periodontitis (a chronic inflammatory disease), is a prominent component of the oral microbiome and a successful colonizer of the oral epithelium. This Gram-negative anaerobe can also exist within the host epithelium without the existence of overt disease. Gingival epithelial cells, the outer lining of the gingival mucosa, which function as an important part of the innate immune system, are among the first host cells colonized by P. gingivalis. This review describes recent studies implicating the co-existence and intracellular adaptation of the organism in these target host cells. Specifically, recent findings on the putative mechanisms of persistence, intercellular dissemination and opportunism are highlighted. These new findings may also represent an original and valuable model for mechanistic characterization of other successful host-adapted, self-limiting, persistent intracellular bacteria in human epithelial tissues.

PMID: 18832296 [PubMed - in process]

Identification of TmcN as a pathway-specific positive regulator of tautomycetin biosynthesis in Streptomyces sp. CK4412.

Microbiology. 2008 Oct;154(Pt 10):2912-9

Authors: Hur YA, Choi SS, Sherman DH, Kim ES

Tautomycetin (TMC) is a novel activated T-cell-specific immunosuppressive compound with a unique structure, containing an ester bond linkage between a terminal cyclic anhydride moiety and a linear polyketide chain bearing an unusual terminal alkene. A 3 kb gene, tmcN, with a deduced product of 1029 amino acid residues, located on the 3'-terminus of an approximately 70 kb contiguous TMC biosynthetic gene cluster, was found to have amino acid sequence homology with bacterial regulatory proteins. In silico database comparisons revealed that TmcN belongs to the large ATP-binding regulators of the LuxR protein family. Gene disruption of tmcN from the Streptomyces sp. CK4412 chromosome resulted in significantly reduced antifungal activity against Aspergillus niger, as well as the absence of TMC. In addition, complementation by an integrative plasmid carrying tmcN restored TMC biosynthesis, strongly suggesting that TmcN is a positive regulator of TMC biosynthesis. Gene expression analysis by RT-PCR of the TMC biosynthetic genes revealed that a TmcN mutant strain exhibited reduced expression levels for most of the biosynthetic genes except for its own tmcN. It is thus suggested that TmcN is a pathway-specific positive regulator that activates transcription of the TMC biosynthetic pathway genes in Streptomyces sp. CK4412.

PMID: 18832298 [PubMed - in process]

The hrp genes of Pseudomonas cichorii are essential for pathogenicity on eggplant but not on lettuce.

Microbiology. 2008 Oct;154(Pt 10):2920-8

Authors: Hojo H, Koyanagi M, Tanaka M, Kajihara S, Ohnishi K, Kiba A, Hikichi Y

Pseudomonas cichorii causes necrotic lesions in eggplant and rot in lettuce. Through transposon insertion into P. cichorii strain SPC9018 we produced two mutants, 4-57 and 2-99, that lost virulence on eggplant but not lettuce. Analyses showed that a transposon was inserted into the hrpG gene in 4-57 and the hrcT gene in 2-99. Nucleotide sequences of the hrp genes of SPC9018 are homologous to those of Pseudomonas viridiflava BS group strains. The pathogenicity of 4-57 on eggplant was restored by transformation with an hrpF operon, originating from either SPC9018 or the BS group member P. viridiflava strain 9504 (Pv9504). These data suggested the involvement of hrp genes in the pathogenicity of SPC9018 on eggplant, and functional conservation of hrpF operons between SPC9018 and Pv9504. Both the hrpS mutant and the hrpL mutant were unable to cause necrotic lesions on eggplant leaves but retained their pathogenicity against lettuce. These results suggest that the pathogenicity of P. cichorii is hrp-dependent in eggplant, but not in lettuce.

PMID: 18832299 [PubMed - in process]

Diversity of IncP-9 plasmids of Pseudomonas.

Microbiology. 2008 Oct;154(Pt 10):2929-41

Authors: Sevastsyanovich YR, Krasowiak R, Bingle LE, Haines AS, Sokolov SL, Kosheleva IA, Leuchuk AA, Titok MA, Smalla K, Thomas CM

IncP-9 plasmids are important vehicles for degradation and resistance genes that contribute to the adaptability of Pseudomonas species in a variety of natural habitats. The three completely sequenced IncP-9 plasmids, pWW0, pDTG1 and NAH7, show extensive homology in replication, partitioning and transfer loci (an approximately 25 kb region) and to a lesser extent in the remaining backbone segments. We used PCR, DNA sequencing, hybridization and phylogenetic analyses to investigate the genetic diversity of 30 IncP-9 plasmids as well as the possibility of recombination between plasmids belonging to this family. Phylogenetic analysis of rep and oriV sequences revealed nine plasmid subgroups with 7-35 % divergence between them. Only one phenotypic character was normally associated with each subgroup, except for the IncP-9beta cluster, which included naphthalene- and toluene-degradation plasmids. The PCR and hybridization analysis using pWW0- and pDTG1-specific primers and probes targeting selected backbone loci showed that members of different IncP-9 subgroups have considerable similarity in their overall organization, supporting the existence of a conserved ancestral IncP-9 sequence. The results suggested that some IncP-9 plasmids are the product of recombination between plasmids of different IncP-9 subgroups but demonstrated clearly that insertion of degradative transposons has occurred on multiple occasions, indicating that association of this phenotype with these plasmids is not simply the result of divergent evolution from a single successful ancestral degradative plasmid.

PMID: 18832300 [PubMed - in process]

Cyclic di-GMP: a second messenger required for long-term survival, but not for biofilm formation, in Mycobacterium smegmatis.

Microbiology. 2008 Oct;154(Pt 10):2942-55

Authors: Kumar M, Chatterji D

Cyclic di-GMP (c-di-GMP) plays an important role in bacterial adaptation to enable survival in changing environments. It orchestrates various pathways involved in biofilm formation, changes in the cell surface, host colonization and virulence. In this article, we report the presence of c-di-GMP in Mycobacterium smegmatis, and its role in the long-term survival of the organism. M. smegmatis has a single bifunctional protein with both GGDEF and EAL domains, which show diguanylate cyclase (DGC) and phosphodiesterase (PDE)-A activity, respectively, in vitro. We named this protein MSDGC-1. Deletion of the gene encoding MSDGC-1 did not affect growth and biofilm formation in M. smegmatis, but long-term survival under conditions of nutritional starvation was affected. Most of the proteins that contain GGDEF and EAL domains have been demonstrated to have either DGC or PDE-A activity. To gain further insight into the regulation of the protein, we cloned the individual domains, and tested their respective activities. MSDGC-1, the full-length protein, is required for activity, as its GGDEF and EAL domains are inactive when separated.

PMID: 18832301 [PubMed - in process]