Biomedical subjects

Ann G Matthysse

Publications and source records attributed to Ann G Matthysse.

8 recordsLinked to original sources

PubMed2005

The effect of cellulose overproduction on binding and biofilm formation on roots by Agrobacterium tumefaciens.

Agrobacterium tumefaciens growing in liquid attaches to the surface of tomato and Arabidopsis thaliana roots, forming a biofilm. The bacteria also colonize roots grown in sterile quartz sand. Attachment, root colonization, and biofilm formation all were markedly reduced in celA and chvB mutants, deficient in production of cellulose and cyclic beta-(1,2)-D-glucans, respectively. We have identified two genes (celG and cell) in which mutations result in the overproduction of cellulose as judged by chemical fractionation and methylation analysis. Wild-type and chvB mutant strains carrying a cDNA clone of a cellulose synthase gene from the marine urochordate Ciona savignyi also overproduced cellulose. The overproduction in a wild-type strain resulted in increased biofilm formation on roots, as evaluated by light microscopy, and levels of root colonization intermediate between those of cellulose-minus mutants and the wild type. Overproduction of cellulose by a nonattaching chvB mutant restored biofilm formation and bacterial attachment in microscopic and viable cell count assays and partially restored root colonization. Although attachment to plant surfaces was restored, overproduction of cellulose did not restore virulence in the chvB mutant strain, suggesting that simple bacterial binding to plant surfaces is not sufficient for pathogenesis.

Agrobacterium tumefaciens↗

PubMed2005

Characterization of the binding of diarrheagenic strains of E. coli to plant surfaces and the role of curli in the interaction of the bacteria with alfalfa sprouts.

Diarrheagenic Escherichia coli were able to bind to plant surfaces, including alfalfa sprouts and open seed coats, and tomato and Arabidopsis thaliana seedlings incubated in water. The characteristics of the binding differed with the bacterial strain examined. Laboratory K12 strains of E. coli failed to show significant binding to any of the plant surfaces examined, suggesting that some of the genes present and expressed in pathogenic strains and absent or unexpressed in K12 strains may be required for binding to plants. When a plasmid carrying the mlrA gene (a positive regulator of curli biosynthesis) or a plasmid carrying the operons that encode the synthesis of curli (csgA-G) was introduced into K12 strains, the bacteria acquired the ability to bind to sprouts. CsgA mutants of an avian pathogenic E. coli and an O157:H7 strain showed no reduction in their ability to bind to sprouts. Thus, the production of curli appears to be sufficient to allow K12 strains to bind, but curli are not necessary for the binding of pathogenic strains, suggesting that pathogenic strains may have more than one mechanism for binding to plant surfaces.

Animals↗

PubMed2005

Differential binding of Escherichia coli O157:H7 to alfalfa, human epithelial cells, and plastic is mediated by a variety of surface structures.

Escherichia coli O157:H7 carried on plant surfaces, including alfalfa sprouts, has been implicated in food poisoning and outbreaks of disease in the United States. Adhesion to cell surfaces is a key component for bacterial establishment and colonization on many types of surfaces. Several E. coli O157:H7 surface proteins are thought to be important for adhesion and/or biofilm formation. Therefore, we examined whether mutations in several genes encoding potential adhesins and regulators of adherence have an effect on bacterial binding to plants and also examined the role of these genes during adhesion to Caco-2 cells and during biofilm formation on plastic in vitro. The genes tested included those encoding adhesins (cah, aidA1, and ompA) and mediators of hyperadherence (tdcA, yidE, waaI, and cadA) and those associated with fimbria formation (csgA, csgD, and lpfD2). The introduction of some of these genes (cah, aidA1, and csg loci) into an E. coli K-12 strain markedly increased its ability to bind to alfalfa sprouts and seed coats. The addition of more than one of these genes did not show an additive effect. In contrast, deletion of one or more of these genes in a strain of E. coli O157:H7 did not affect its ability to bind to alfalfa. Only the absence of the ompA gene had a significant effect on binding, and the plant-bacterium interaction was markedly reduced in a tdcA ompA double mutant. In contrast, the E. coli O157:H7 ompA and tdcA ompA mutant strains were only slightly affected in adhesion to Caco-2 cells and during biofilm formation. These findings suggest that some adhesins alone are sufficient to promote binding to alfalfa and that they may exist in E. coli O157:H7 as redundant systems, allowing it to compensate for the loss of one or more of these systems. Binding to the three types of surfaces appeared to be mediated by overlapping but distinct sets of genes. The only gene which appeared to be irreplaceable for binding to plant surfaces was ompA.

Adhesins, Bacterial↗

PubMed2004

A functional cellulose synthase from ascidian epidermis.

Among animals, urochordates (e.g., ascidians) are unique in their ability to biosynthesize cellulose. In ascidians cellulose is synthesized in the epidermis and incorporated into a protective coat know as the tunic. A putative cellulose synthase-like gene was first identified in the genome sequences of the ascidian Ciona intestinalis. We describe here a cellulose synthase gene from the ascidian Ciona savignyi that is expressed in the epidermis. The predicted C. savignyi cellulose synthase amino acid sequence showed conserved features found in all cellulose synthases, including plants, but was most similar to cellulose synthases from bacteria, fungi, and Dictyostelium discoidium. However, unlike other known cellulose synthases, the predicted C. savignyi polypeptide has a degenerate cellulase-like region near the carboxyl-terminal end. An expression construct carrying the C. savignyi cDNA was found to restore cellulose biosynthesis to a cellulose synthase (CelA) minus mutant of Agrobacterium tumefaciens, showing that the predicted protein has cellulose synthase activity. The lack of cellulose biosynthesis in all other groups of metazoans and the similarity of the C. savignyi cellulose synthase to enzymes from cellulose-producing organisms support the hypothesis that the urochordates acquired the cellulose biosynthetic pathway by horizontal transfer.

Agrobacterium tumefaciens↗

PubMed2004

The FNR-type transcriptional regulator SinR controls maturation of Agrobacterium tumefaciens biofilms.

Agrobacterium tumefaciens is a plant pathogen that persists as surface-associated populations on plants or soil particles. A genetic screen for A. tumefaciens mutants deficient for surface interactions identified a mutant that forms thin, sparsely populated biofilms, but is proficient for initial attachment. The mutant is disrupted in a gene designated sinR, encoding a member of the DNR subfamily of FNR-type transcription regulators. SinR is required for normal maturation of A. tumefaciens biofilms on both inert surfaces and plant tissues, and elevated sinR expression results in accelerated biofilm formation. Expression of sinR is increased close to 30-fold in cultures grown in oxygen-limited environments and is also induced within biofilms grown under oxic conditions. A consensus FNR box, the presumptive binding site for FNR-type proteins, is located upstream of the sinR promoter. FnrN, a second A. tumefaciens FNR-like regulator, is required for induction of sinR in oxygen-limited cultures, whereas SinR negatively influences its own expression. FnrN influences biofilm formation, but its effects are less dramatic than those of SinR. We propose a model in which a signal cascade, responsive to oxygen limitation and initiated by FnrN, activates sinR expression in response to decreased oxygen levels, and influences the formation of A. tumefaciens biofilms.

Agrobacterium tumefaciens↗

PubMed2003

Identification of Arabidopsis rat mutants.

Limited knowledge currently exists regarding the roles of plant genes and proteins in the Agrobacterium tumefaciens-mediated transformation process. To understand the host contribution to transformation, we carried out root-based transformation assays to identify Arabidopsis mutants that are resistant to Agrobacterium transformation (rat mutants). To date, we have identified 126 rat mutants by screening libraries of T-DNA insertion mutants and by using various "reverse genetic" approaches. These mutants disrupt expression of genes of numerous categories, including chromatin structural and remodeling genes, and genes encoding proteins implicated in nuclear targeting, cell wall structure and metabolism, cytoskeleton structure and function, and signal transduction. Here, we present an update on the identification and characterization of these rat mutants.

Agrobacterium tumefaciens↗

PubMed2003

Agrobacterium-mediated root transformation is inhibited by mutation of an Arabidopsis cellulose synthase-like gene.

Agrobacterium-mediated plant genetic transformation involves a complex interaction between the bacterium and the host plant. Relatively little is known about the role plant genes and proteins play in this process. We previously identified an Arabidopsis mutant, rat4, that is resistant to Agrobacterium transformation. We show here that rat4 contains a T-DNA insertion into the 3'-untranslated region of the cellulose synthase-like gene CSLA9. CSLA9 transcripts are greatly reduced in the rat4 mutant. Genetic complementation of rat4 with wild-type genomic copies of the CSLA9 gene restores both transformation competence and the wild-type level of CSLA9 transcripts. The CSLA9 promoter shows a distinct pattern of expression in Arabidopsis plants. In particular, the promoter is active in the elongation zone of roots, the root tissue that we previously showed is most susceptible to Agrobacterium-mediated transformation. Disruption of the CSLA9 gene in the rat4 mutant results in reduced numbers and rate of growth of lateral roots and reduced ability of the roots to bind A. tumefaciens cells under certain conditions. No major differences in the linkage structure of the non-cellulosic polysaccharides could be traced to the defective CSLA9 gene.

Agrobacterium tumefaciens↗

PubMed2002

Attachment to roots and virulence of a chvB mutant of Agrobacterium tumefaciens are temperature sensitive.

Agrobacterium tumefaciens chvB mutants are unable to produce beta-1,2 glucan. They are nonattaching and avirulent and show reduced motility at room temperature. At lower temperatures (16 degrees C), chvB mutants became virulent on Bryophyllum daigremontiana and Lycopersicon esculentum and were able to attach to L. esculentum, Arabidopsis thaliana, Daucus carota, and Tagetes erecta roots. The mutant bacteria also recovered wild-type motility at lower temperatures. Two other nonattaching mutants of A. tumefaciens, AttR and AtrA, were unaffected by the lowered temperature, remaining nonattaching and avirulent.

Agrobacterium tumefaciens↗