Browsing by Subject "biofilms"
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Item Effect of CSLM imaging rate on biofilms of P. aeruginosa and S. aureus(2015-05) Du, Reginald; Gordon, VernitaBiofilms are sessile communities of bacteria that can be found in an wide range of environments. Their inhabitants are phenotypically distinct from plank- tonic bacteria and are capable of forming complex, three-dimensional structures. Biofilms are studied using confocal scanning laser microscopy, or CSLM. This technique uses lasers and Novel Fluorescent Proteins (NFPs) to measure growth and structure formation of single- and multi-species biofilms in situ in three dimensions. We investigate the effects of slow and fast rates of image acquisition on mono- and co-cultures of biofilm forming bacteria: Pseudomonas aeruginosa and Staphylococcus aureus. After calculating growth rates and lag times, we find that fast scanning rates reduce the growth rate of P. aeruginosa in co-culture. Additionally, co-culture speeds up P. aeruginosa growth relative to monoculture when imaged at a slow rate, and fast scanning reverts co-culture growth to monoculture-like behavior. Additionally, a significant lag time is observed for P. aeruginosa grown in co-culture. The observed influence of confocal imaging rate on population dynamics should be considered in future studies to ensure accurate measurement of bacterial phenomena.Item First Evidence for the Presence of Iron Oxidizing Zetaproteobacteria at the Levantine Continental Margins(PLOS One, 2014-03-10) Rubin-Blum, Maxim; Antler, Gilad; Tsadok, Rami; Shemesh, Eli; Austin Jr., James A.; Coleman, Dwight F.; Goodman-Tchernov, Beverly N.; Ben-Avraham, Zvi; Tchernov, DanDuring the 2010–2011 E/V Nautilus exploration of the Levantine basin’s sediments at the depth of 300–1300 m, densely patched orange-yellow flocculent mats were observed at various locations along the continental margin of Israel. Cores from the mat and the control locations were collected by remotely operated vehicle system (ROV) operated by the E/V Nautilus team. Microscopic observation and phylogenetic analysis of microbial 16S and 23S rRNA gene sequences indicated the presence of zetaproteobacterial stalk forming Mariprofundus spp. – like prokaryotes in the mats. Bacterial tag-encoded FLX amplicon pyrosequencing determined that zetaproteobacterial populations were a dominant fraction of microbial community in the biofilm. We show for the first time that zetaproteobacterial may thrive at the continental margins, regardless of crustal iron supply, indicating significant fluxes of ferrous iron to the sediment-water interface. In light of this discovery, we discuss the potential bioavailability of sediment-water interface iron for organisms in the overlying water column.Item Pseudomonas aeruginosa Enhances Production of a Non-Alginate Exopolysaccharide during Long-Term Colonization of the Cystic Fibrosis Lung(PLOS One, 2013-12-06) Huse, Holy K.; Kwon, Taejoon; Zlosnik, James E.A.; Speert, David P.; Marcotte, Edward M.; Whiteley, MarvinThe gram-negative opportunistic pathogen Pseudomonas aeruginosa is the primary cause of chronic respiratory infections in individuals with the heritable disease cystic fibrosis (CF). These infections can last for decades, during which time P. aeruginosa has been proposed to acquire beneficial traits via adaptive evolution. Because CF lacks an animal model that can acquire chronic P. aeruginosa infections, identifying genes important for long-term in vivo fitness remains difficult. However, since clonal, chronological samples can be obtained from chronically infected individuals, traits undergoing adaptive evolution can be identified. Recently we identified 24 P. aeruginosa gene expression traits undergoing parallel evolution in vivo in multiple individuals, suggesting they are beneficial to the bacterium. The goal of this study was to determine if these genes impact P. aeruginosa phenotypes important for survival in the CF lung. By using a gain-of-function genetic screen, we found that 4 genes and 2 operons undergoing parallel evolution in vivo promote P. aeruginosa biofilm formation. These genes/operons promote biofilm formation by increasing levels of the non-alginate exopolysaccharide Psl. One of these genes, phaF, enhances Psl production via a post-transcriptional mechanism, while the other 5 genes/operons do not act on either psl transcription or translation. Together, these data demonstrate that P. aeruginosa has evolved at least two pathways to over-produce a non-alginate exopolysaccharide during long-term colonization of the CF lung. More broadly, this approach allowed us to attribute a biological significance to genes with unknown function, demonstrating the power of using evolution as a guide for targeted genetic studies.