Publications (5) View all
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Article: Mycobacterium gilvum illustrates size-correlated mycobacteria Acanthamoeba polyphaga relationships.
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ABSTRACT: Mycobacteria are isolated from soil and water environments where free-living amoeba are living. Free-living amoeba are bactericidal, yet some rapidly-growing mycobacteria are amoeba-resistant organisms surviving in the amoebal trophozoites and cysts. Such capacity has not been studied for the environmental rapidly-growing Mycobacterium gilvum. We investigated the ability of M. gilvum to survive in the trophozoites of Acanthamoeba polyphaga strain Linc-AP1 by using optic and electron microscopy and culture-based microbial enumerations in the presence of negative controls. We observed that 29% of A. polyphaga cells were infected by M. gilvum mycobacteria 6-hour post-infection. Survived M. gilvum mycobacteria did not multiply and did not kill the amoebal trophozoites during five-day co-culture. Extensive electron microscopy observation indicated that M. gilvum measured 1.4 ± 0.5 μm, and failed to find M. gilvum organisms into the amoebal cysts. Further experimental study of two other rapidly-growing mycobacteria Mycobacterium rhodesiae and Mycobacterium thermoresistible indicated that both measured < 2 μm and exhibited same amoeba-mycobacteria relationships as M. gilvum. In general, we observed that mycobacteria measuring < 2 μm significantly do not grow within and do not kill amoebal trophozoites comparing to mycobacteria measuring > 2 μm (p < 0.05). The mechanisms underlying such observation remain to be determined.Applied and environmental microbiology 12/2012; · 3.69 Impact Factor -
Article: Genetic engineering of Mycobacterium tuberculosis: a review.
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ABSTRACT: Genetic engineering has been used for decades to mutate and delete genes in the Mycobacterium tuberculosis genome with the translational goal of producing attenuated mutants with conserved susceptibility to antituberculous antibiotics. The development of plasmids and mycobacteriophages that can transfer DNA into the M. tuberculosis chromosome has effectively overcome M. tuberculosis slow growth rate and the capsule and mycolic acid wall, which limit DNA uptake. The use of genetic engineering techniques has shed light on many aspects of pathogenesis mechanisms, including cellular growth, mycolic acid biosynthesis, metabolism, drug resistance and virulence. Moreover, such research gave clues to the development of new vaccines or new drugs for routine clinical practice. The use of genetic engineering tools is mainly based on the underlying concept that altering or reducing the M. tuberculosis genome could decrease its virulence. A contrario, recent post-genomic analyses indicated that reduced bacterial genomes are often associated with increased bacterial virulence and that M. tuberculosis acquired genes by lateral genetic exchange during its evolution. Therefore, ancestors utilizing genetic engineering to add genes to the M. tuberculosis genome may lead to new vaccines and the availability of M. tuberculosis isolates with increased susceptibility to antituberculous antibiotics.Tuberculosis (Edinburgh, Scotland) 07/2012; 92(5):365-76. · 2.54 Impact Factor -
Article: Acanthamoeba polyphaga-enhanced growth of Mycobacterium smegmatis.
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ABSTRACT: Mycobacterium smegmatis is a rapidly-growing mycobacterium causing rare opportunistic infections in human patients. It is present in soil and water environments where free-living amoeba also reside, but data regarding M. smegmatis-amoeba relationships have been contradictory from mycobacteria destruction to mycobacteria survival. Using optic and electron microscopy and culture-based microbial enumeration we investigated the ability of M. smegmatis mc(2) 155, M. smegmatis ATCC 19420(T) and M. smegmatis ATCC 27204 organisms to survive into Acanthamoeba polyphaga trophozoites and cysts. We observed that M. smegmatis mycobacteria penetrated and survived in A. polyphaga trophozoites over five-day co-culture resulting in amoeba lysis and the release of viable M. smegmatis mycobacteria without amoebal cyst formation. We further observed that amoeba-co-culture, and lysed amoeba and supernatant and pellet, significantly increased five-day growth of the three tested M. smegmatis strains, including a four-fold increase in intra-amoebal growth. Amoebal co-culture increases the growth of M. smegmatis resulting in amoeba killing by replicating M. smegmatis mycobacteria. This amoeba-M. smegmatis co-culture system illustrates an unusual paradigm in the mycobacteria-amoeba interactions as mycobacteria have been mainly regarded as amoeba-resistant organisms. Using these model organisms, this co-culture system could be used as a simple and rapid model to probe mycobacterial factors implicated in the intracellular growth of mycobacteria.PLoS ONE 01/2012; 7(1):e29833. · 4.09 Impact Factor -
Article: The genealogic tree of mycobacteria reveals a long-standing sympatric life into free-living protozoa.
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ABSTRACT: Free-living protozoa allow horizontal gene transfer with and between the microorganisms that they host. They host mycobacteria for which the sources of transferred genes remain unknown. Using BLASTp, we searched within the genomes of 15 mycobacteria for homologous genes with 34 amoeba-resistant bacteria and the free-living protozoa Dictyostelium discoideum. Subsequent phylogenetic analysis of these sequences revealed that eight mycobacterial open-reading frames (ORFs) were probably acquired via horizontal transfer from beta- and gamma-Proteobacteria and from Firmicutes, but the transfer histories could not be reliably established in details. One further ORF encoding a pyridine nucleotide disulfide oxidoreductase (pyr-redox) placed non-tuberculous mycobacteria in a clade with Legionella spp., Francisella spp., Coxiella burnetii, the ciliate Tetrahymena thermophila and D. discoideum with a high reliability. Co-culturing Mycobacterium avium and Legionella pneumophila with the amoeba Acanthamoeba polyphaga demonstrated that these two bacteria could live together in amoebae for five days, indicating the biological relevance of intra-amoebal transfer of the pyr-redox gene. In conclusion, the results of this study support the hypothesis that protists can serve as a source and a place for gene transfer in mycobacteria.PLoS ONE 01/2012; 7(4):e34754. · 4.09 Impact Factor -
Article: Oxygen reduction in the strict anaerobe Desulfovibrio vulgaris Hildenborough: characterization of two membrane-bound oxygen reductases.
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ABSTRACT: Although Desulfovibrio vulgaris Hildenborough (DvH) is a strictly anaerobic bacterium, it is able to consume oxygen in different cellular compartments, including extensive periplasmic O₂ reduction with hydrogen as electron donor. The genome of DvH revealed the presence of cydAB and cox genes, encoding a quinol oxidase bd and a cytochrome c oxidase, respectively. In the membranes of DvH, we detected both quinol oxygen reductase [inhibited by heptyl-hydroxyquinoline-N-oxide (HQNO)] and cytochrome c oxidase activities. Spectral and HPLC data for the membrane fraction revealed the presence of o-, b- and d-type haems, in addition to a majority of c-type haems, but no a-type haem, in agreement with carbon monoxide-binding analysis. The cytochrome c oxidase is thus of the cc(o/b)o₃ type, a type not previously described. The monohaem cytochrome c₅₅₃ is an electron donor to the cytochrome c oxidase; its encoding gene is located upstream of the cox operon and is 50-fold more transcribed than coxI encoding the cytochrome c oxidase subunit I. Even when DvH is grown under anaerobic conditions in lactate/sulfate medium, the two terminal oxidase-encoding genes are expressed. Furthermore, the quinol oxidase bd-encoding genes are more highly expressed than the cox genes. The cox operon exhibits an atypical genomic organization, with the gene coxII located downstream of coxIV. The occurrence of these membrane-bound oxygen reductases in other strictly anaerobic Deltaproteobacteria is discussed.Microbiology 07/2011; 157(Pt 9):2720-32. · 3.06 Impact Factor
