Mark C Black

Publications (2)5.76 Total impact

• Article: Genomic and biological analysis of phage Xfas53 and related prophages of Xylella fastidiosa.

  Elizabeth J Summer, Christopher J Enderle, Stephen J Ahern, Jason J Gill, Cruz P Torres, David N Appel, Mark C Black, Ry Young, Carlos F Gonzalez
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  ABSTRACT: We report the plaque propagation and genomic analysis of Xfas53, a temperate phage of Xylella fastidiosa. Xfas53 was isolated from supernatants of X. fastidiosa strain 53 and forms plaques on the sequenced strain Temecula. Xfas53 forms short-tailed virions, morphologically similar to podophage P22. The 36.7-kb genome is predicted to encode 45 proteins. The Xfas53 terminase and structural genes are related at a protein and gene order level to P22. The left arm of the Xfas53 genome has over 90% nucleotide identity to multiple prophage elements of the sequenced X. fastidiosa strains. This arm encodes proteins involved in DNA metabolism, integration, and lysogenic control. In contrast to Xfas53, each of these prophages encodes head and DNA packaging proteins related to the siphophage lambda and tail morphogenesis proteins related to those of myophage P2. Therefore, it appears that Xfas53 was formed by recombination between a widespread family of X. fastidiosa P2-related prophage elements and a podophage distantly related to phage P22. The lysis cassette of Xfas53 is predicted to encode a pinholin, a signal anchor and release (SAR) endolysin, and Rz and Rz1 equivalents. The holin gene encodes a pinholin and appears to be subject to an unprecedented degree of negative regulation at both the level of expression, with rho-independent transcriptional termination and RNA structure-dependent translational repression, and the level of holin function, with two upstream translational starts predicted to encode antiholin products. A notable feature of Xfas53 and related prophages is the presence of 220- to 390-nucleotide degenerate tandem direct repeats encoding putative DNA binding proteins. Additionally, each phage encodes at least two BroN domain-containing proteins possibly involved in lysogenic control. Xfas53 exhibits unusually slow adsorption kinetics, possibly an adaptation to the confined niche of its slow-growing host.
  Journal of bacteriology 11/2009; 192(1):179-90. · 3.94 Impact Factor
• Source

  Available from: uttyler.edu

  Article: Initial genetic analysis of Xylella fastidiosa in Texas.

  Lisa D Morano, Blake R Bextine, Dennis A Garcia, Shermel V Maddox, Stanley Gunawan, Natalie J Vitovsky, Mark C Black
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  ABSTRACT: Xylella fastidiosa is the causative agent of Pierce's Disease of grape. No published record of X. fastidiosa genetics in Texas exists despite growing financial risk to the U.S. grape industry, a Texas population of the glassy-winged sharpshooter insect vector (Homalodisca vitripennis) now spreading in California, and evidence that the bacterium is ubiquitous to southern states. Using sequences of conserved gyrB and mopB genes, we have established at least two strains in Texas, grape strain and ragweed strain, corresponding genetically with subsp. piercei and multiplex, respectively. The grape strain in Texas is found in Vitis vinifera varieties, hybrid vines, and wild Vitis near vineyards, whereas the ragweed strain in Texas is found in annuals, shrubs, and trees near vineyards or other areas. RFLP and QRT PCR techniques were used to differentiate grape and ragweed strains with greater efficiency than sequencing and are practical for screening numerous X. fastidiosa isolates for clade identity.
  Current Microbiology 05/2008; 56(4):346-51. · 1.82 Impact Factor