FEMS Microbiology Letters

Bald, Dirk; Koul, Anil

doi: 10.1111/j.1574-6968.2010.01959.xpmid: 20402785

AbstractMycobacterium tuberculosis, the causative agent of tuberculosis, poses a global health challenge due to the emergence of drug-resistant strains. Recently, bacterial energy metabolism has come into focus as a promising new target pathway for the development of antimycobacterial drugs. This review summarizes our current knowledge on mycobacterial respiratory energy conversion, in particular, during the physiologically dormant state that is associated with latent or persistent tuberculosis infections. Targeting components of respiratory ATP production, such as type-2 NADH dehydrogenase or ATP synthase, is illustrated as an emerging strategy in the development of novel drugs.

Lizier, Michela; Sarra, Pier G.; Cauda, Roberto; Lucchini, Franco

doi: 10.1111/j.1574-6968.2010.01978.xpmid: 20455948

AbstractThe synthesis of heterologous proteins in lactobacilli is strongly influenced by the promoter selected for the expression. In addition, the activity of the promoters themselves may vary among different bacterial hosts. Three different promoters were investigated for their capability to drive enhanced green fluorescent protein (EGFP) expression in Lactococcus lactis spp. cremoris MG1363, in Lactobacillus reuteri DSM 20016T and in five L. reuteri strains isolated from chicken crops. The promoters of the Lactobacillus acidophilus surface layer protein gene (slp), L. acidophilus lactate dehydrogenase gene (ldhL) and enterococcal rRNA adenine N-6-methyltransferase gene (ermB) were fused to the coding sequence of EGFP and inserted into the backbone of the pTRKH3 shuttle vector (pTRKH3-slpGFP, pTRKH3-ldhGFP, pTRKH3-ermGFP). Besides conventional analytical methods, a new quick fluorimetric approach was set up to quantify the EGFP fluorescence in transformed clones using the Qubit™ fluorometer. ermB proved to be the most effective promoter in L. reuteri isolates, producing 3.90 × 10−7 g of fluorescent EGFP (mL ODstationary culture)−1. Under the same conditions, the ldhL promoter produced 2.66 × 10−7 g of fluorescent EGFP (mL ODstationary culture)−1. Even though the slp promoter was efficient in L. lactis spp. cremoris MG1363, it was nearly inactive both in L. reuteri DSM 20016T and in L. reuteri isolates.

Soto-Suárez, Mauricio; González, Carolina; Piégu, Benoît; Tohme, Joe; Verdier, Valérie

doi: 10.1111/j.1574-6968.2010.01985.xpmid: 20487016

AbstractXanthomonas oryzae pathovar oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc) cause bacterial diseases in rice: leaf blight and leaf streak, respectively. Although both the Asian and the African strains of Xoo induce similar symptoms, they are genetically different, with the African Xoo strains being more closely related to the Asian Xoc. To identify the sequences responsible for differences between African and Asian Xoo strains and their relatedness to Xoc strains, a suppression-subtractive hybridization (SSH) procedure was performed, using the African Xoo MAI1 strain as a tester and the Philippine Xoo PXO86 strain and Xoc BLS256 strain as drivers. A nonredundant set of 134 sequences from MAI1 was generated. Several DNA fragments isolated by SSH were similar to genes of unknown function, hypothetical proteins, genes related to the type III secretion system, and other pathogenicity-related genes. The specificity of various fragments was validated by Southern blot analysis. SSH sequences were compared with several xanthomonad genomes. In silico analysis revealed SSH sequences as specific to strain MAI1, revealing their potential as specific markers for further epidemiological and diagnostic studies. SSH proved to be a useful method for rapidly identifying specific genes among closely related X. oryzae strains.

Mata, Caterina; Miró, Elisenda; Mirelis, Beatriz; Garcillán-Barcia, Maria Pilar; De La Cruz, Fernando; Coll, Pere; Navarro, Ferran

doi: 10.1111/j.1574-6968.2010.01980.xpmid: 20487017

AbstractWe report a Serratia marcescens and an Escherichia coli isolate simultaneously detected in the same patient. Both isolates showed susceptibility patterns suggestive of harbouring a plasmid-mediated AmpC β-lactamase (pACBL) and a plasmid-encoded quinolone resistance (PMQR). PCR-based replicon, MOB typing, plasmid profile and Southern hybridization analyses revealed that both isolates coharboured blaDHA-1 and qnrB genes on the same IncL/M-MOBP13 plasmid approximately 70 kb in size. Together with the fact that both plasmids were conjugative in the laboratory, these results strongly suggest that a horizontal transfer event could take place in vivo. This is the first report of an isolate of S. marcescens harbouring a pACBL. The only phenotypic method that suggests the presence of a pACBL in an isolate harbouring an inducible chromosomal AmpC enzyme is the observation of scattered colonies near the edge of the inhibition zones of some β-lactams. The presence of both resistance genes on the same plasmid and the reported increase in PMQR could perhaps explain the widespread distribution of blaDHA-1 genes.

Haridas, Sajeet; Gantt, J. Stephen

doi: 10.1111/j.1574-6968.2010.01979.xpmid: 20455947

AbstractWe present the 91 500 bp mitochondrial genome of the wood-degrading basidiomycete Trametes cingulata and compare it with the mitochondrial genomes of five additional Basidiomycota species. The Trametes mitochondrial genome encodes 15 proteins, 25 tRNAs and the small and large rRNAs. All of the genes, except one tRNA, are found on the same DNA strand. Several additional ORFs have also been identified; however, their sequences have not been conserved across the species we compared and they show no similarity to any known gene, suggesting that they may not correspond to authentic genes. The presence of endonuclease-like sequences in introns suggests a mechanism that explains the diversity of mitochondrial genome sizes that are unrelated to the gene content.

Manzano, Marisa; Giusto, Cristina; Iacumin, Lucilla; Patthey, Chiara; Cecchini, Francesca; Fontanillas, Ramon; Comi, Giuseppe

doi: 10.1111/j.1574-6968.2010.01984.xpmid: 20455950

AbstractRainbow trout gastroenteritis has been related to the accumulation of segmented filamentous bacteria in the digestive tract of fish, which presents lethargy, reduced appetite and accumulation of mucoid faeces. Some authors associate the comparison of illness with the presence of viable filaments, which produce and release strings of endospores in the lumen of the gut. The segmented filamentous bacteria that could not be cultured in vitro have been related to Clostridium group I, and they have been named Candidatus arthromitus. Despite the various strategies that have been used to detect unculturable microorganisms, molecular methods have facilitated studies on culture-independent microorganisms. Direct DNA extraction from samples and subsequent study of 16S rRNA genes represent a tool for studying unculturable microbial flora. As direct detection of specific microorganisms is possible through the utilization of primers or probes annealing specific DNA sequences, the aim of this work was to design specific primers for the direct detection of C. arthromitus in fish using a nested PCR.

Huergo, Luciano F.; Noindorf, Lilian; Gimenes, Camila; Lemgruber, Renato S.P.; Cordellini, Daniela F.; Falarz, Lucas J.; Cruz, Leonardo M.; Monteiro, Rose A.; Pedrosa, Fábio O.; Chubatsu, Leda S.; Souza, Emanuel M.; Steffens, Maria B.R.

Smits, Theo H.M.; Rezzonico, Fabio; Pelludat, Cosima; Goesmann, Alexander; Frey, Jürg E.; Duffy, Brion

doi: 10.1111/j.1574-6968.2010.01994.xpmid: 20487014

AbstractA 530-kb megaplasmid pPag3 contributing 10.8% of the total genome of Pantoea vagans biocontrol strain C9-1 was sequenced. A rare nonpigmented variant C9-1W was obtained and shown to have lost pPag3, but retained all other plasmids (pPag1, pPag2). Phenotypic characterization of the variant confirmed the function of several annotated genes that may influence ecological fitness and efficacy. Metabolic profiling revealed important plasmid-based carbon utilization phenotypes. Plasmid loss resulted in thiamine auxotrophy, absence of carotenoid pigmentation, desferrioxamine diffusible siderophore biosynthesis, inherent ampicillin resistance and expression of AI-1 quorum-sensing signaling. This confirmed the functional expression of the corresponding genes located on pPag3 in P. vagans.

Trofimova, Yuliya; Walker, Graeme; Rapoport, Alexander

doi: 10.1111/j.1574-6968.2010.01989.xpmid: 20487021

AbstractThe influence of calcium and magnesium ions on resistance to dehydration in the yeast, Saccharomyces cerevisiae, was investigated. Magnesium ion availability directly influenced yeast cells' resistance to dehydration and, when additionally supplemented with calcium ions, this provided further significant increase of yeast resistance to dehydration. Gradual rehydration of dry yeast cells in water vapour indicated that both magnesium and calcium may be important for the stabilization of yeast cell membranes. In particular, calcium ions were shown for the first time to increase the resistance of yeast cells to dehydration in stress-sensitive cultures from exponential growth phases. It is concluded that magnesium and calcium ion supplementations in nutrient media may increase the dehydration stress tolerance of S. cerevisiae cells significantly, and this finding is important for the production of active dry yeast preparations for food and fermentation industries.

Feng, Peter C.H.; Keys, Christine; Lacher, David; Monday, Steven R.; Shelton, Dan; Rozand, Christine; Rivas, Marta; Whittam, Thomas

doi: 10.1111/j.1574-6968.2010.01990.xpmid: 20487015

AbstractWe examined O157:non-H7 strains isolated from various sources and geographical locations and found 15/57 strains to carry eae alleles, including α, β, ɛ and κ/δ, suggesting that these strains may be prevalent. All strains were serologically and genetically confirmed to be O157, but none were the H7 serotype or carried any trait virulence factors of the Escherichia coli O157:H7 serotype. Genetic H typing of the eae-positive strains showed that the α-eae-bearing strain was H45, while the β- and ɛ-eae strains were H16 and the κ/δ-eae strains were H39. The β- and ɛ-eae-bearing O157:H16 strains shared ∼90% pulsed-field gel electrophoresis (PFGE) similarity and were distinct from the other strains that had other eae alleles. Interestingly, an ɛ-eae O157:H16 strain isolated from meat in France shared PFGE similarity to the O157:H16 strains from water in the United States. Multilocus sequence typing showed that there is clonal diversity within the O157 serogroup, as some O157:non-H7 strains clustered with EPEC clonal groups, while others clustered within the ST-171 group of diverse strains and serotypes that had not previously included any strains from the O157 serogroup. Clonal analysis also showed that none of the eae-positive O157:non-H7 strains we examined were closely related to the pathogenic O157:H7 serotype.