Biofilms colonization

Sobczak, W. V. 1996. Epilithic bacterial responses to variations in algal biomass and labile dissolved organic carbon during biofilm colonization. Journal of the North American Benthological Society 15 143-154. 

Pend) a J, Avci R, Geesey GG, Stoodley P, Hamilton M, Harkin G (1996) Chemical effect of biofilm colonization on 304 stainless steel. J Vac Sci Technol A14 1955-1760... 

Macfarlane, S. and Macfarlane, G.T. (2006) Composition and metabolic activities of bacterial biofilms colonizing food residues in the human gut. Appl Environ Microbiol 72, 6204-6211. 

Many of the by-products of microbial metaboHsm, including organic acids and hydrogen sulfide, are corrosive. These materials can concentrate in the biofilm, causing accelerated metal attack. Corrosion tends to be self-limiting due to the buildup of corrosion reaction products. However, microbes can absorb some of these materials in their metaboHsm, thereby removing them from the anodic or cathodic site. The removal of reaction products, termed depolari tion stimulates further corrosion. Figure 10 shows a typical result of microbial corrosion. The surface exhibits scattered areas of localized corrosion, unrelated to flow pattern. The corrosion appears to spread in a somewhat circular pattern from the site of initial colonization. 

When fouling occurs, even mechanical cleaning does not remove all traces of the bio film. Previously fouled and cleaned surfaces are more rapidly colonized than new surfaces. Residual biofilm materials promote colonization and reduce the lag time before significant fouling reappears. 

MIC depends on the complex structure of corrosion products and passive films on metal surfaces as well as on the structure of the biofilm. Unfortunately, electrochemical methods have sometimes been used in complex electrolytes, such as microbiological culture media, where the characteristics and properties of passive films and MIC deposits are quite active and not fully understood. It must be kept in mind that microbial colonization of passive metals can drastically change their resistance to film breakdown by causing localized changes in the type, concentration, and thickness of anions, pH, oxygen gradients, and inhibitor levels at the metal surface during the course of a... 

The biosphere includes ecological niches where microbes peacefully co-exist with their eukaryotic host in the human this includes the concept of the micro-biome [14], which is defined as the totality of microbial organisms that co-habit with human beings. On the other hand, microbial colonization of human mucosal surfaces or prosthetic devices, often results in the development of biofilms, with significant deleterious effects on human health [15]. These are some of the challenges in infectious diseases that reflect the need to maximally utilize genomic sequence information and related sciences to better control microbial disease in human populations, and to develop anti-microbial agents with a better therapeutic index. 

During start-up, the microbial population distribution in the biofilm varies with time. Initial colonization of the particle may be by one or more species that alter the surface favorably for colonization by other species. For instance, in the operation of a butyrate-degrading fluidized bed bioreactor, methanogens attached to the sand particles early in the start-up process and produced a primary matrix of heteropolysaccharides that allowed attachment of other bacterial species (Sreekrishnan et al., 1991 Zellner et al., 1991 Yongming et al., 1993). This is contrary to findings in an acetate-propionate-butyrate degrading reactor, in which facultative anaerobes were found to be the initial colonizers (Lauwers et al., 1990). 

The choice of solid carriers spans a wide spectrum (Table 1) from materials most suitable for research purposes (sintered glass beads, laterite stone deposited on a gramophone disk) to industrial materials (pumice, activated carbon, etc.). Key properties that affect the performance of the carrier are porosity (from impervious to controlled-size pores), composition (from ceramics to activated carbon), and hydrophilic behavior. It is difficult to perform a direct comparison of different carriers. Colonization and biofilm growth depend strongly on the nature of bacteria and on their intrinsic propensity to adhere on hydrophilic vs. hydrophobic surfaces. 

Aside from adding defined compounds, experimental additions of natural DOM mixtures suspected to vary in lability have helped test ideas about the contribution of various DOM sources to aquatic ecosystems. In a nice example using manipulation of natural DOM sources, Battin et al. (1999) used flowthrough microcosms to measure the relative uptake rates of allochthonous and autochthonous DOM by stream sediments. They documented greater than fivefold differences or more in uptake and respiration, depending on whether the DOM was extracted from soil or periphyton. Moreover, they were able to show, via transplant experiments, several cases where prior exposure to a particular source of DOM increased the ability of that community to metabolize the DOM supplied. There appears to be some preadaptation of microbial catabolic capacity when these stream biofilms were re-exposed to a familiar type of DOM. Similarly, the response of heterotrophic bacteria to carbon or nutrient addition was greatest when the source community was particularly active (Foreman et al., 1998). Kaplan et al. (1996) showed that fixed film bioreactors, colonized on one water source, were unable to rapidly metabolize DOC in water from another source. 

Unprotected surfaces submersed in water eventually become colonized by bacteria and various flora and fauna that may ultimately form a biofilm (Figure 3.3). 

B. Colonization Attachment, Surface Motility, and Biofilm Formation.375... 

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. ... 

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