Virginia Chow

University of Florida, Gainesville, Florida, United States

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Publications (6)19.02 Total impact

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    ABSTRACT: Paenibacillus sp. strain JDR-2, an aggressively xylanolytic bacterium isolated from sweetgum (Liquidambar styraciflua) wood, is able to efficiently depolymerize, assimilate and metabolize 4-O-methylglucuronoxylan, the predominant structural component of hardwood hemicelluloses. A basis for this capability was first supported by the identification of genes and characterization of encoded enzymes and has been further defined by the sequencing and annotation of the complete genome, which we describe. In addition to genes implicated in the utilization of β-1,4-xylan, genes have also been identified for the utilization of other hemicellulosic polysaccharides. The genome of Paenibacillus sp. JDR-2 contains 7,184,930 bp in a single replicon with 6,288 protein-coding and 122 RNA genes. Uniquely prominent are 874 genes encoding proteins involved in carbohydrate transport and metabolism. The prevalence and organization of these genes support a metabolic potential for bioprocessing of hemicellulose fractions derived from lignocellulosic resources.
    Standards in Genomic Sciences 03/2012; 6(1):1-10. · 3.17 Impact Factor
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    ABSTRACT: Bacterial spot of tomato and pepper is caused by four Xanthomonas species and is a major plant disease in warm humid climates. The four species are distinct from each other based on physiological and molecular characteristics. The genome sequence of strain 85-10, a member of one of the species, Xanthomonas euvesicatoria (Xcv) has been previously reported. To determine the relationship of the four species at the genome level and to investigate the molecular basis of their virulence and differing host ranges, draft genomic sequences of members of the other three species were determined and compared to strain 85-10. We sequenced the genomes of X. vesicatoria (Xv) strain 1111 (ATCC 35937), X. perforans (Xp) strain 91-118 and X. gardneri (Xg) strain 101 (ATCC 19865). The genomes were compared with each other and with the previously sequenced Xcv strain 85-10. In addition, the molecular features were predicted that may be required for pathogenicity including the type III secretion apparatus, type III effectors, other secretion systems, quorum sensing systems, adhesins, extracellular polysaccharide, and lipopolysaccharide determinants. Several novel type III effectors from Xg strain 101 and Xv strain 1111 genomes were computationally identified and their translocation was validated using a reporter gene assay. A homolog to Ax21, the elicitor of XA21-mediated resistance in rice, and a functional Ax21 sulfation system were identified in Xcv. Genes encoding proteins with functions mediated by type II and type IV secretion systems have also been compared, including enzymes involved in cell wall deconstruction, as contributors to pathogenicity. Comparative genomic analyses revealed considerable diversity among bacterial spot pathogens, providing new insights into differences and similarities that may explain the diverse nature of these strains. Genes specific to pepper pathogens, such as the O-antigen of the lipopolysaccharide cluster, and genes unique to individual strains, such as novel type III effectors and bacteriocin genes, have been identified providing new clues for our understanding of pathogen virulence, aggressiveness, and host preference. These analyses will aid in efforts towards breeding for broad and durable resistance in economically important tomato and pepper cultivars.
    BMC Genomics 03/2011; 12:146. · 4.40 Impact Factor
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    ABSTRACT: Paenibacillus sp. strain JDR-2, an aggressively xylanolytic bacterium isolated from decaying sweet gum wood, secretes a multimodular glycohydrolase family GH10 endoxylanase (XynA1) anchored to the cell surface. The gene encoding XynA1 is part of a xylan utilization regulon that includes an aldouronate utilization gene cluster with genes encoding a GH67 alpha-glucuronidase (AguA), a GH10 endoxylanase (XynA2), and a GH43 arabinofuranosidase/beta-xylosidase (XynB). Here we show that this Paenibacillus sp. strain is able to utilize methylglucuronoxylose (MeGAX(1)), an aldobiuronate product that accumulates during acid pretreatment of lignocellulosic biomass, and methylglucuronoxylotriose (MeGAX(3)), the product of the extracellular XynA1 acting on methylglucuronoxylan (MeGAX(n)). The average rates of utilization of MeGAX(n), MeGAX(1), and MeGAX(3) were 149.8, 59.4, and 54.3 microg xylose equivalents.ml(-1).h(-1), respectively, and were proportional to the specific growth rates on the substrates. AguA was active with MeGAX(1) and MeGAX(3), releasing 4-O-methyl-d-glucuronate alpha-1,2 linked to a nonreducing terminal xylose residue. XynA2 converted xylotriose, generated by the action of AguA on MeGAX(3), to xylose and xylobiose. The ability to utilize MeGAX(1) provides a novel metabolic potential for bioconversion of acid hydrolysates of lignocellulosics. The 2.8-fold-greater rate of utilization of polymeric MeGAX(n) than that of MeGAX(3) indicates that there is coupling of extracellular depolymerization, assimilation, and intracellular metabolism, allowing utilization of lignocellulosics with minimal pretreatment. Along with adjacent genes encoding transcriptional regulators and ABC transporter proteins, the aguA and xynA2 genes in the cluster described above contribute to the efficient utilization of aldouronates derived from dilute acid and/or enzyme pretreatment protocols applied to the conversion of hemicellulose to biofuels and chemicals.
    Applied and Environmental Microbiology 05/2009; 75(13):4410-8. · 3.95 Impact Factor
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    Virginia Chow, Guang Nong, James F Preston
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    ABSTRACT: Direct bacterial conversion of the hemicellulose fraction of hardwoods and crop residues to biobased products depends upon extracellular depolymerization of methylglucuronoxylan (MeGAX(n)), followed by assimilation and intracellular conversion of aldouronates and xylooligosaccharides to fermentable xylose. Paenibacillus sp. strain JDR-2, an aggressively xylanolytic bacterium, secretes a multimodular cell-associated GH10 endoxylanase (XynA1) that catalyzes depolymerization of MeGAX(n) and rapidly assimilates the principal products, beta-1,4-xylobiose, beta-1,4-xylotriose, and MeGAX(3), the aldotetrauronate 4-O-methylglucuronosyl-alpha-1,2-xylotriose. Genomic libraries derived from this bacterium have now allowed cloning and sequencing of a unique aldouronate utilization gene cluster comprised of genes encoding signal transduction regulatory proteins, ABC transporter proteins, and the enzymes AguA (GH67 alpha-glucuronidase), XynA2 (GH10 endoxylanase), and XynB (GH43 beta-xylosidase/alpha-arabinofuranosidase). Expression of these genes, as well as xynA1 encoding the secreted GH10 endoxylanase, is induced by growth on MeGAX(n) and repressed by glucose. Sequences in the yesN, lplA, and xynA2 genes within the cluster and in the distal xynA1 gene show significant similarity to catabolite responsive element (cre) defined in Bacillus subtilis for recognition of the catabolite control protein (CcpA) and consequential repression of catabolic regulons. The aldouronate utilization gene cluster in Paenibacillus sp. strain JDR-2 operates as a regulon, coregulated with the expression of xynA1, conferring the ability for efficient assimilation and catabolism of the aldouronate product generated by a multimodular cell surface-anchored GH10 endoxylanase. This cluster offers a desirable metabolic potential for bacterial conversion of hemicellulose fractions of hardwood and crop residues to biobased products.
    Journal of bacteriology 01/2008; 189(24):8863-70. · 3.94 Impact Factor
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    ABSTRACT: Pasteuria species are endospore-forming obligate bacterial parasites of soil-inhabiting nematodes and water-inhabiting cladocerans, e.g. water fleas, and are closely related to Bacillus spp. by 16S rRNA gene sequence. As naturally occurring bacteria, biotypes of Pasteuria penetrans are attractive candidates for the biocontrol of various Meloidogyne spp. (root-knot nematodes). Failure to culture these bacteria outside their hosts has prevented isolation of genomic DNA in quantities sufficient for identification of genes associated with host recognition and virulence. We have applied multiple-strand displacement amplification (MDA) to generate DNA for comparative genomics of biotypes exhibiting different host preferences. Using the genome of Bacillus subtilis as a paradigm, MDA allowed quantitative detection and sequencing of 12 marker genes from 2000 cells. Meloidogyne spp. infected with P. penetrans P20 or B4 contained single nucleotide polymorphisms (SNPs) in the spoIIAB gene that did not change the amino acid sequence, or that substituted amino acids with similar chemical properties. Individual nematodes infected with P. penetrans P20 or B4 contained SNPs in the spoIIAB gene sequenced in MDA-generated products. Detection of SNPs in the spoIIAB gene in a nematode indicates infection by more than one genotype, supporting the need to sequence genomes of Pasteuria spp. derived from single spore isolates.
    FEMS Microbiology Ecology 09/2007; 61(2):327-36. · 3.56 Impact Factor
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    ABSTRACT: The subject invention provides at least one nucleic acid sequence encoding an aldouronate-utilization regulon isolated from Paenibacillus sp. strain JDR-2, a bacterium which efficiently utilizes xylan and metabolizes aldouronates (methylglucuronoxylosaccharides). The subject invention also provides a means for providing a coordinately regulated process in which xylan depolymerization and product assimilation are coupled in Paenibacillus sp. strain JDR-2 to provide a favorable system for the conversion of lignocellulosic biomass to biobased products. Additionally, the nucleic acid sequences encoding the aldouronate-utilization regulon can be used to transform other bacteria to form organisms capable of producing a desired product (e.g., ethanol, 1-butanol, acetoin, 2,3-butanediol, 1,3-propanediol, succinate, lactate, acetate, malate or alanine) from lignocellulosic biomass.