Defining Genetic Fitness Determinants and Creating Genomic Resources for an Oral Pathogen.

Periodontitis is a microbial infection that destroys the structures that support the teeth. Although it is typically a chronic condition, rapidly progressing, aggressive forms are associated with the oral pathogen One of this bacterium's key virulence traits is its ability to attach to surfaces and form robust biofilms that resist killing by the host and antibiotics. Though much has been learned about since its initial discovery, we lack insight into a fundamental aspect of its basic biology, as we do not know the full set of genes that it requires for viability (the essential genome).

Staphylococcus aureus Shifts toward Commensalism in Response to Corynebacterium Species.

Staphylococcus aureus-human interactions result in a continuum of outcomes from commensalism to pathogenesis. S. aureus is a clinically important pathogen that asymptomatically colonizes ~25% of humans as a member of the nostril and skin microbiota, where it resides with other bacteria including commensal Corynebacterium species.

Pheromone killing of multidrug-resistant Enterococcus faecalis V583 by native commensal strains.

Multidrug-resistant Enterococcus faecalis possess numerous mobile elements that encode virulence and antibiotic resistance traits as well as new metabolic pathways, often constituting over one-quarter of the genome. It was of interest to determine how this large accretion of mobile elements affects competitive growth in the gastrointestinal (GI) tract consortium. We unexpectedly observed that the prototype clinical isolate strain V583 was actively killed by GI tract flora, whereas commensal enterococci flourished.

Transcriptional response of Enterococcus faecalis to sunlight.

Microarrays were used to investigate the transcriptional response of Enterococcus faecalis to photostress. E. faecalis are Gram-positive bacteria used as indicators of water quality and have been shown to vary diurnally in response to sunlight.

Short-term adhesion and long-term biofouling testing of polydopamine and poly(ethylene glycol) surface modifications of membranes and feed spacers for biofouling control.

Ultrafiltration, nanofiltration membranes and feed spacers were hydrophilized with polydopamine and polydopamine-g-poly(ethylene glycol) surface coatings. The fouling propensity of modified and unmodified membranes was evaluated by short-term batch protein and bacterial adhesion tests. The fouling propensity of modified and unmodified membranes and spacers was evaluated by continuous biofouling experiments in a membrane fouling simulator.

Discovery of a biofilm electrocline using real-time 3D metabolite analysis.

Bacteria are social organisms that possess multiple pathways for sensing and responding to small molecules produced by other microbes. Most bacteria in nature exist in sessile communities called biofilms, and the ability of biofilm bacteria to sense and respond to small molecule signals and cues produced by neighboring biofilm bacteria is particularly important. To understand microbial interactions between biofilms, it is necessary to perform rapid, real-time spatial quantification of small molecules in microenvironments immediately surrounding biofilms; however, such measurements have been elusive.

Metabolite cross-feeding enhances virulence in a model polymicrobial infection.

Microbes within polymicrobial infections often display synergistic interactions resulting in enhanced pathogenesis; however, the molecular mechanisms governing these interactions are not well understood. Development of model systems that allow detailed mechanistic studies of polymicrobial synergy is a critical step towards a comprehensive understanding of these infections in vivo. In this study, we used a model polymicrobial infection including the opportunistic pathogen Aggregatibacter actinomycetemcomitans and the commensal Streptococcus gordonii to examine the importance of metabolite cross-feeding for establishing co-culture infections.

Real-time mapping of a hydrogen peroxide concentration profile across a polymicrobial bacterial biofilm using scanning electrochemical microscopy.

Quantitative detection of hydrogen peroxide in solution above a Streptococcus gordonii (Sg) bacterial biofilm was studied in real time by scanning electrochemical microscopy (SECM). The concentration of hydrogen peroxide was determined to be 0.7 mM to 1.

Polymicrobial interactions stimulate resistance to host innate immunity through metabolite perception.

Bacteria in the human oral cavity often grow in an attached multispecies biofilm community. Members of this community display defined interactions that have an impact on the physiology of the individual and the group. Here, we show that during coculture growth with streptococci, the oral pathogen Aggregatibacter actinomycetemcomitans displays enhanced resistance to killing by host innate immunity.

Pseudomonas aeruginosa attachment and biofilm development in dynamic environments.

Biofilm formation by Pseudomonas aeruginosa is hypothesized to follow a developmental pattern initiated by attachment to a surface followed by microcolony formation and mature biofilm development. Swimming and twitching motility are important for attachment and biofilm development in P. aeruginosa.

Differential expression of Desulfovibrio vulgaris genes in response to Cu(II) and Hg(II) toxicity.

The response of Desulfovibrio vulgaris to Cu(II) and Hg(II) was characterized. Both metals increased the lag phase, and Cu(II) reduced cell yield at concentrations as low as 50 microM. mRNA expression was analyzed using random arbitrarily primed PCR, differential display, and quantitative PCR.