KEVIN F DYBVIG

..These data cast doubt on the prevailing paradigms that restriction systems are either selfish or function to confer protection from invasion by foreign DNA...

..This study also revealed evidence of gene duplications in M. pulmonis and identified chromosome segregation proteins that are dispensable in mycoplasmas but essential in Bacillus subtilis...

..Of the 635 predicted coding regions, 218 were disrupted in a library of 1,100 members. Dispensable genes included the gene coding for the MAM superantigen and genes coding for ribosomal proteins S15, S18, and L15...

..Genomic data indicate that the cassette was acquired by horizontal gene transfer and possibly located on a mobile element...

..These results may be pertinent to understanding the functions of similar proteins that have extensive repeat regions in other microbes...

..Tn4001T may be of general utility for use as a mycoplasma cloning vehicle because tetM functions in all species of Mycoplasma examined thus far...

..Confounding the interpretation of these results is the observation that the mutants missing EPS-I had an eightfold overproduction of an apparent second EPS (EPS-II) containing N-acetylglucosamine...

..As variation in the number of Vsa tandem repeats occurs by slipped-strand mispairing, the ability of the mycoplasmas to form a biofilm switches stochastically...

..This tracheal organ-mounting system can be used to study interactions between biofilms formed by respiratory pathogens and the host epithelium and to identify the factors that contribute to biofilm formation in vivo...

..The resistance appeared to be localized to those mycoplasmas within tower structures of the biofilms. Biofilm formation may be a mechanism that protects mycoplasmas from host immunity...

..As both VsaH and VsaA can mediate adherence to plastic, cytadherence, and susceptibility to complement, we propose that Vsa modulates these phenotypes by nonspecific interactions...

..pulmonis surface interactions and function to sterically hinder access of complement to the mycoplasma cell membrane while permitting access of smaller molecules...

..A mutant with a defect in transport of N-acetylglucosamine was identified...

..The data strongly indicate that Vsa phase variation is a mechanism for avoidance of the immune system with no obvious contribution to tissue tropism...

..Vir had no effect on MAV1 adsorption. We conclude that Vir is not a virulence factor but functions to exclude superinfecting phage, possibly by blocking the injection of phage DNA into the bacterial cytoplasm...

..The degree of mitogenic activity correlated with lethal toxicity in DBA/2J mice. In contrast, histopathological studies detected no correlation between MAM production and the severity of arthritis induced in DBA/2J and CBA/J mice...

..Analysis of the progeny indicated that only the transposon and not flanking genomic DNA was transferred to the recipient cell. Gene transfer was DNase resistant and probably the result of conjugation or cell fusion...

..The virulence of 158 and 158-1 did not increase upon lysogenization. A major antigenic difference between 158 and 158-1 was identified that is unrelated to MAV1 and could account for the difference in virulence...

..These data indicate that the nucleotides 5" of the GAA repeats as well as the spacing between the GAA repeats and sequences downstream (3") of the repeats are important for pMGA gene expression...

..Specifically, the MAV1 lysogen 158L3-1 was more virulent than the nonlysogen strain 158 in DBA/2NCr, C3H/HeNCr, C3H/HeJ, and C3Smn.CB17-Prkdc(scid)/J mice, as well as in LEW rats...

..Thus, HvsR is a site-specific DNA recombinase with dual substrate specificity...

..Transformation of M. arthritidis was not significantly affected by modification of plasmid at HhaI sites, indicating that the mycoplasma lacks a restriction endonuclease that recognizes GCGC sites...

..By understanding the role of repetitive proteins in the disease process, it is anticipated that improved measures to control the infections of these significant human pathogens will be developed. ..

..Mutants that do not survive will be characterized further to determine whether their defect is a failure to grow in vivo, to adhere to the epithelium, or to resist host defenses. ..

..An understanding of the inability of 158-1 to resist host defenses may offer an unique opportunity to explore interactions between the mycoplasma and innate immunity. ..

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..arthritidis chromosome and/or specifically mutated to construct strains that will be examined for arthritogenicity in the rat model and used to conclusively identify the MAV1 genes that are involved in the development of arthritis. ..

..The fifth and final aim is to expand our repertoire of subclones containing DNA inversions and other rearrangements in order to more fully characterize the potential for genetic variation in this system. ..

..arthritidis by affecting interactions with host factors such as B and T cells and complement. Thus, the process of dissecting the function of MAV1 in virulence will be begun. ..

..In aim 2, mutants with defects in putative DNA recombinases and V-I protein production will be examined to study the mechanisms of gene rearrangements and phenotypic switching. ..

..By understanding the role of repetitive proteins in the disease process, it is anticipated that improved measures to control the infections of these significant human pathogens will be developed. ..