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Mycoplasma genitalium is the smallest self-replicating organism and a successful human pathogen associated with a range of genitourinary maladies. As a consequence of its restricted genome size, genes that are highly conserved in other bacteria are absent in M. genitalium. Significantly, genes that encode antioxidants like superoxide dismutase and catalase-peroxidase are lacking. Nevertheless, comparative genomics has revealed that MG 454 of M. genitalium encodes a protein with putative function as an organic hydroperoxide reductase (Ohr). In this study, we found that an M. genitalium transposon mutant that lacks expression of MG_454 was sensitive to killing by t-butyl hydroperoxide and cumene hydroperoxide. To understand whether this sensitivity to hydroperoxides was linked to MG_454, we cloned this gene behind an arabinose-inducible PBAD promoter in plasmid pHERD20T and transformed this construct (pHERDMG454) into a Pseudomonas aeruginosa strain having deletion in its ohr gene (ohr mutant) and showing sensitivity to organic hydroperoxides. The P. aeruginosa ohr mutant harboring pHERDMG454, when induced with arabinose, was able to reverse its sensitivity to organic hydroperoxides, thus supporting the notion that the product of MG_454 resists organic hydroperoxides in M. genitalium. Surprisingly, real-time reverse transcription-PCR showed that expression of MG_454 in M. genitalium was not elevated in response to oxidative stress but was elevated in response to physical stresses, like salt (NaCl) and heat. Although failure of MG_454 to respond to oxidative stress in M. genitalium implies the absence of a known oxidative stress response regulator in the genome of M. genitalium, elevated expression of MG_454 due to physical stress suggests its control by an unidentified regulator. doi: 10.1128/JB.01066-08

The serine cycle methylotroph Methylobacterium extorquens AM1 contains two pterin-dependent pathways for [C.sub.1] transfers, the tetrahydrofolate ([H.sub.4]F) pathway and the tetrahydromethanopterin ([H.sub.4]MPT) pathway, and both are required for growth on [C.sub.1] compounds. With the exception of formate-tetrahydrofolate ligase (FtfL, alternatively termed formyl-[H.sub.4]F synthetase), all of the genes encoding the enzymes comprising these two pathways have been identified, and the corresponding gene products have been purified and characterized. We present here the purification and characterization of FtfL from M. extorquens AM1 and the confirmation that this enzyme is encoded by an ftfL homolog identified previously through transposon mutagenesis. Phenotypic analyses of the ftfL mutant strain demonstrated that FtfL activity is required for growth on [C.sub.1] compounds. Unlike mutants defective for the [H.sub.4]MPT pathway, the ftfL mutant strain does not exhibit phenotypes indicative of defective formaldehyde oxidation. Furthermore, the ftfL mutant strain remained competent for wild-type conversion of [[sup.14]C] methanol to [[sup.14]C] C[O.sub.2]. Collectively, these data confirm our previous presumptions that the [H.sub.4]F pathway is not the key formaldehyde oxidation pathway in M. extorquens AM1. Rather, our data suggest an alternative model for the role of the [H.sub.4]F pathway in this organism in which it functions to convert formate to methylene [H.sub.4]F for assimilatory metabolism.

A total of 12 VanA-type vancomycin-resistant enterococci, consisting of 10 Enterococcus faecium isolates and two Enterococcus avium isolates, were examined in detail. The vancomycin resistance conjugative plasmids pHT[alpha] (65.9 kbp), pHT[Beta] (63.7 kbp), and pHT[gamma] (66.5 kbp) were isolated from each of three different E. faecium strains. The plasmids transferred highly efficiently between enterococcus strains during broth mating and were homologous with pMG1 ([Gm.sup.r]; 65.1 kb).

A new group of transposable elements, which the authors have named cryptons, was detected in several pathogenic fungi, including the basidiomycete Cryptococcus neoformans, and the ascomycetes Coccidioides posadasii and Histoplasma capsulatum. These elements are unlike any previously described transposons. An archetypal member of the group, crypton Cn1, is 4 kb in length and is present at a low but variable copy number in a variety of C. neoformans strains. It displays interstrain variations in its insertion sites, suggesting recent mobility. The internal region contains a long gene, interrupted by several introns. The product of this gene contains a putative tyrosine recombinase near its middle, and a region similar in sequence to the DNA-binding domains of several fungal transcription factors near its C-terminus. The element contains no long repeat sequences, but is bordered by short direct repeats which may have been produced by its insertion into the host genome by recombination. Many of the structural features of crypton Cn1 are conserved in the other known cryptons, suggesting that these elements represent the functional forms. The presence of cryptons in ascomycetes and basidiomycetes suggests that this is an ancient group of elements (> 400 million years old). Sequence comparisons suggest that cryptons may be related to the DIRS1 and Ngaro 1 groups of tyrosine-recombinase-encoding retrotransposons.

Edwardsiella tarda causes haemorrhagic septicaemia in fish and gastro-and extra-intestinal infections in animals including humans. Resistance to phagocyte-mediated killing is one of the virulence factors of Ed. tarda. The authors' previous studies using TnphoA transposon mutagenesis indicated that katB mutants derived from the strain PPD130/91 are at least 1.6 log higher in L[D.sub.50] values than the wild-type strain. These findings suggest the involvement of catalase (KatB) in Ed. tarda pathogenesis. In this study, experiments were conducted to characterize the contribution of KatB to Ed. tarda infection. Zymographic analyses indicated that the 22 Ed. tarda strains examined expressed three different types of catalase-peroxidases (Kat1-3) based on their mobility in non-denaturing polyacrylamide gels. KatB (Kat1), the major catalase enzyme, was expressed in eight out of 22 Ed. tarda strains, and was commonly found in virulent strains except AL9379. AL9379 has a mutated katB, which has a base substitution and a deletion that translate into stop codons in the catalase gene. KatB produced by PPD130/91 was located in both periplasmic and cytoplasmic fractions and was constitutively expressed in various growth phases. Kinetics studies indicated that the catalase provided resistance to [H.sub.2][O.sub.2]-and phagocyte-mediated killing. Infection kinetics studies of katB mutant 34 in gourami fish demonstrated its inability to survive and replicate in phagocyte-rich organs and this prevented the dissemination of infections when compared to the wild-type. Complementation of catalase mutants restored the production of catalase, and led to an increase in the resistance to [H.sub.2][O.sub.2]-and phagocyte-mediated killing, and a decrease in L[D.sub.50] values. This study has identified and characterized a major catalase gene (katB) that is required for resistance to [H.sub.2][O.sub.2]-and phagocyte-mediated killing in Ed. tarda. The results also suggest that catalase may play a role as a virulence factor in Ed. tarda pathogenesis.

The bacterial strain Delftia acidovorans P4a, isolated from an extreme environment (heavily contaminated with organochlorines, highly alkaline conditions in an aqueous environment), was found to mineralize 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid under alkaline conditions. Screening a genomic DNA library of the alkalitolerant strain for 2,4-D genes revealed the presence of the two 2,4-D gene clusters tfdCDEF and tfd[C.sub.II][E.sub.II]BKA, tfdR genes being located in the vicinity of each tfd gene cluster. The results showed that the putative genes of the complete 2,4-D degradation pathway are organized in a single genomic unit. Sequence similarities to homologous gene clusters indicate that the individual tfd elements of strain P4a do not share a common origin, but were brought together by recombination events. The entire region is flanked by insertion elements of the IS1071 and IS1380 families, forming a transposon-like structure of about 30 kb, of which 28.4 kb were analysed. This element was shown to be located on the bacterial chromosome. The present study provides the first reported case of a chromosomally located catabolic transposon which carries the genes for the complete 2,4-D degradation pathway.

Research has been conducted on DEH transposon from Pseudomonas putida strain PP3. The function, the structure of this transposon and the full sequence of DEH element, including ISPpu12, have been investigated, and the results from the experiments studying its transposition and associated effects are presented.

Research has been conducted on Pseudomonas putida mt-2 archetypal tolyene-xylene catabolic plasmid pWW0. The identification of the insertion sequence ISPpu12 on this plasmid has been carried out, and the details are reported.

Research has been conducted on Bacillus thuringiensis strains. Bacillus thuringiensis acrystalliferrous mutant strain which produces brown soluble pigment identified as beta-exotoxin I has been investigated, and the results demonstrate that the genes involed in beta-exotoxin I production have been identified via the use of the random mutant library and the mini-transposon delivery system.

Research has been conducted on biphenyl catabolic transposon Tn4371. The authors report that they have completed and analyzed nucleotide sequence of this transposon, and that it has a mosaic structure composed of several building blocks.

The authors review the publications on pathogenic bacteria. The topics of interest include conjugative transfer in unicellular gram-positive bacteria, in mycelium-forming streptomycetes and in other actinobacteria.

Research has been conducted on Escherichia coli insertion elements IS3, IS150 and IS186. The authors demonstrate that these elements can produce transpositionally active heat-to-tail dimers with the structure and transpositional activity similar to the dimers of IS2, IS21 and IS30.

Research has been conducted on intracellulart opportunistic pathogen Rhodococcus equi. The use of the transposon mutagenesis system developed by the authors and the application of Himar1 minitransposon produced by conditionally replicating plasmid for construction of R. equi mutants are described.

Research has been conducted on facultative methylotroph Methylobacterium extorquens AM1. The identification of methylotrophy genes of this bacterium has been carried out from a transposon mutagenesis screen, and the results demonstrate that one of these genes encodes a product which is identical to dihydrofolate reductase.

Research has been conducted on the ability of bacteria to reduce selenate and selenite into less toxic elemental selenium. The mechanisms of the reduction and transport of selenium oxyanions in Escherichia coli have been investigated via the use of genetic analysis and transposon mutagenesis, and the results are reported.

Research has been conducted on Tn5041 transposons discovered among mercury resistant environmental Gram-negative strains. The study of georgaphic distribution, evolutionary relationship and molecular divercity of Tn5041 transposon variants has been carried out in investigating mercury resistance gene flow in environmetal bacteria, and the details are reported.