Biofilm formation in Desulfovibrio vulgaris Hildenborough is dependent upon protein filaments

Abstract

Desulfovibrio vulgaris Hildenborough is a Gram-negative sulfate-reducing bacterium (SRB), and the physiology of SRBs can impact many anaerobic environments including radionuclide waste sites, oil reservoirs and metal pipelines. In an attempt to understand D. vulgaris as a population that can adhere to surfaces, D. vulgaris cultures were grown in a defined medium and analysed for carbohydrate production, motility and biofilm formation. Desulfovibrio vulgaris wild-type cells had increasing amounts of carbohydrate into stationary phase and approximately half of the carbohydrate remained internal. In comparison, a mutant that lacked the 200 kb megaplasmid, strain DeltaMP, produced less carbohydrate and the majority of carbohydrate remained internal of the cell proper. To assess the possibility of carbohydrate re-allocation, biofilm formation was investigated. Wild-type cells produced approximately threefold more biofilm on glass slides compared with DeltaMP; however, wild-type biofilm did not contain significant levels of exopolysaccharide. In addition, stains specific for extracellular carbohydrate did not reveal polysaccharide material within the biofilm. Desulfovibrio vulgaris wild-type biofilms contained long filaments as observed with scanning electron microscopy (SEM), and the biofilm-deficient DeltaMP strain was also deficient in motility. Biofilms grown directly on silica oxide transmission electron microscopy (TEM) grids did not contain significant levels of an exopolysaccharide matrix when viewed with TEM and SEM, and samples stained with ammonium molybdate also showed long filaments that resembled flagella. Biofilms subjected to protease treatments were degraded, and different proteases that were added at the time of inoculation inhibited biofilm formation. The data indicated that D. vulgaris did not produce an extensive exopolysaccharide matrix, used protein filaments to form biofilm between cells and silica oxide surfaces, and the filaments appeared to be flagella. It is likely that D. vulgaris used flagella for more than a means of locomotion to a surface, but also used flagella, or modified flagella, to establish and/or maintain biofilm structure.

Plasmodium falciparum Merozoite Surface Protein 3

“…The amyloid coat on the merozoite surface was described as patches of regular denticulation in early schizogony and later formed long bristles and filaments that appeared thicker at apices than their stems and thus suggested the presence of a complex formation (42). Interestingly, similar filamentous extracellularly extended structures have also been reported in many eukaryotic and prokaryotic cells termed adhesins, extracellular appendages, fibrils, and filaments (43)(44)(45)(46). However, the components of merozoite's amyloid coat have remained unexplored so far.…”

Mechanism of Uranium Reduction and Immobilization in Desulfovibrio vulgaris Biofilms

“…This timeline was selected on the basis of our observation and previous studies reporting visible D. vulgaris biofilm formation 15 h after inoculation. 34 This strategy enabled us to examine the behavior of uranium with coexisting microbial activity and a variety of reducing agents under varying carbonate concentrations (5 mM for the mixed system and 30 mM for the biotic system). In the abiotic system, the biofilm was allowed to fully develop (4 days) and produce reduced iron and sulfur species before biomass inactivation and uranium addition.…”

Syntrophic Growth of Desulfovibrio alaskensis Requires Genes for H 2 and Formate Metabolism as Well as Those for Flagellum and Biofilm Formation

“…Syntrophic cultures also can transfer electrons directly between the two species using filamentous structures (9). Aggregates of pure cultures of D. vulgaris occurring in biofilms show a flagellum-like structure, which appears to connect cells together (12,14). The composition of the latter filaments have not been identified nor has a role for flagella been proven in the syntrophic interaction.…”

“…Such is the case in many anaerobic environments where the degradation of alcohols, fatty and alicyclic acids, and aromatic compounds is thermodynamically possible only when the electron-accepting partner maintains very low H 2 or formate concentrations (11). Because these compounds are only degraded by syntrophic consortia under methanogenic conditions, the net free energy available from the overall reaction, which is typically small, must be shared between both partners (9,(12)(13)(14)(15).…”

“…Such is the case in many anaerobic environments where the degradation of alcohols, fatty and alicyclic acids, and aromatic compounds is thermodynamically possible only when the electron-accepting partner maintains very low H 2 or formate concentrations (11). Because these compounds are only degraded by syntrophic consortia under methanogenic conditions, the net free energy available from the overall reaction, which is typically small, must be shared between both partners (9,(12)(13)(14)(15).To date, syntrophic organisms have been shown to be either strictly fermentative (e.g., Syntrophus aciditrophicus and Syntrophomonas wolfei) or those capable of syntrophy in the absence of a terminal electron-accepting process (e.g., Geobacter and Desulfovibrio) (9, 16). The electron-accepting organisms are often methanogens (3), but sulfate-reducing (16) and fumarate-reducing organisms (9) have been shown to function efficiently with H 2 and/or formate-producing syntrophic metabolizers.…”