Biofilm bacteria

M. J. Franklin, D. E. Nivens, A. A. Vass, M. W. Mittelman, R. F. Jack, M. J. E. Dowling, and D. C. White. Effect of chlorine and chlorine/bromine biocide treatments on the number and activity of biofilm bacteria and on carbon steel corrosion. Corrosion, 47(2) 128-134, February 1991. 

Physical methods for the control of microbial biofilms, although often effective, are in many situations impractical. In this context it is notable that an almost universal feature of the biofilm mode of growth is their profound resistance to antibacterial compounds. Conventional chemical control methods, developed for use against fastgrowing planktonic cultures are only poorly effective against biofilm bacteria. Large doses of biocide or antibiotics, which are either environmentally undesirable or above toxic thresholds respectively, are required to eradicate biofilms in industry and medicine. 

In order to understand current approaches for prevention and control of biofilms, we must first consider the reasons for the failure of conventional antimicrobial protocols. There are thought to be three main reasons as to why biofilm bacteria out-survive their planktonic counterparts during antimicrobial treatments (reviewed by McBain et a/.16).These are i) poor penetration of antimicrobial compounds due to the presence and turn-over of exopolymer slime (glycocalyx) ii) the imposition of extreme nutrient limitation within the depths of the biofilm community and the co-incident expression of metabolically-dormant, recalcitrant phenotypes and (iii) the expression of attachment-specific phenotypes that are radically different and intrinsically less susceptible than unattached ones. 

Flocculins and especially Flo 11 are responsible for morphogenic phenomena such as pseudohyphal growth and biofilm formation in yeast. Biofilm formation is an adhesive phenomenon akin to flocculation. The majority of bacteria exist in highly organized natural biofilm populations rather than in free floating cultures. Within the biofilm, bacteria display coordinated behavior. They form structures, release toxins or emit light. They, sometimes, differentiate to form physiologically defined... 

Other cultivation strategies which were followed were the enrichment of picoplankton bacteria under a wide range of nutrient and incubation conditions [33], and isolation of biofilm bacteria that had grown in situ on artificial surfaces. 

The resident microbes within the mouth readily form biofilms on teeth. A biofilm consists of a population of bacteria coexisting in an orderly structure at the interface of a solid and a liquid [14] and, within a biofilm, bacteria living in colonies encapsulated in a matrix of extracellular polymer. Oral biofilms are known to vary extensively in structure throughout the colony, with regions of densely packed microorganisms surrounded by open water channels. Each type of bacteria exists in reasonably defined environments which are influenced by surrounding cells, distance from the outer surface and local structure, all of which influence availability of nutrients and ambient pH. 

Most biofilm bacteria grow as a monospecies, in dense microcolonies, adjacent to other species of cooperative organisms, all held within a less dense matrix. 

Ellis, B. D., P. Butterfield, W. L. Jones, G. A. McFeters, and A. K. Camper. 2000. Effects of carbon source, carbon concentration, and chlorination on growth related parameters of heterotrophic biofilm bacteria. Microbial Ecology 38 330-347. 

III. Supply of Dissolved Organic Matter to Biofilm Bacteria 289... 

III. SUPPLY OF DISSOLVED ORGANIC MATTER TO BIOFILM BACTERIA... 

Because of the high area of solid surfaces covered with biofilms, these biofilms dominate the heterotrophic metabolism in many aquatic ecosystems. In streams, rivers, and shallow lakes, bacterial activity in epilithic and epiphytic biofilms may be several times higher on an areal basis than the activity of free living bacteria. By the differential use of specific DOM fractions, biofilm bacteria influence the biogeochemical composition of DOM in these ecosystems. Biofilms thus can control biogeochemical fluxes of DOM and are important sinks of organic matter. 

Mittelman, M. W. 1999. Recovery and characterization of biofilm bacteria associated with medical devices. In Biofilms (R. J. Doyle, Ed.), Methods in Enzymology, Vol. 310, pp. 534-551. Academic Press, San Diego. 

Whiteley, M., J. R. Ott, E. A. Weaver, and R. J. C. McLean. 2001. Effects of community composition and growth rate on aquifer biofilm bacteria and their susceptibility to betadine disinfection. Environmental Microbiology 3 43-52. 

Herrmann194 196 was able to stimulate metamorphosis in Phoronis muelleri and P. psammophila with dense suspensions of bacteria. It is impossible to know if these results are indicative of a natural response to biofilm bacteria in the field. 

The role of biofilm bacteria in barnacle settlement has been a topic of considerable investigation and discussion (see Sections II and III.C above). Despite numerous studies finding positive associations between biofilms and the settlement of barnacle cyprid larvae, Roberts et al.,198 using shortterm field tests of treated surfaces, found, Although bacterial films can have dramatic effects on settlement of barnacles and bryozoans...they are not essential for colonization by barnacles, bryo-zoans or hydroids. ... 

Definitive chemical analyses of the nature of compounds produced by biofilm bacteria that induce settlement and metamorphosis of invertebrates are generally lacking. Peptides, supposedly arising from biofilm bacteria and having the capacity to induce settlement of oyster larvae, were described by Zimmer-Faust and Tamburri18 (discussed above in Section III.C). Studies of larval settlement in the spirorbid polychaete Janua brasiliensis have indicated that its alga-specific settlement is, in fact, mediated by carbohydrate moieties of the exopolymers of biofilm bacteria.173... 

Biofilm bacteria are also notorious for being highly resistant to antimicrobial agents. Some possible explanations are listed as follows (Cloete, 2003) ... 

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