Adhering biofilm

Recently, there has developed a greater recognition of the complexity of the MIC process. MIC is rarely hnked to a unique mechanism or to a single species of microorganisms. At the present state of knowledge, it is widely accepted that the growth of different microbial species within adherent biofilms facihtates the development of structured consortia that may enhance the microbial effects on corrosion. 

On these coupons, protection from surface oxidation may possibly have been provided by a tightly adhered biofilm or by some coating left over from coupon manufacturing. The existence of a biofilm on aluminium coupons has been shown in other microbiological characterization work done in the RBOF [1.12]. No localized attack was observed in these passivated areas of the coupon. 

Here, we discuss an optimized DNA extraction method specifically for electrode-adhered biofilm communities. We describe the use of a biofilm DNA extraction kit from MoBio Laboratories Inc. to extract DNA from electrode-adhered communities (PowerBiofilm DNA Isolation Kit, www.mobio.com). Here, we included a slightly modified alternative for cell lysis to include less meehanical bead-beating and multiple heat treatments. This method for cell lysis has been found to be successful for electrogenic community analyses [18, 21], We do not endorse MoBio Laboratories. This protocol is solely meant to be a starting point for researchers. 

In many countries it is compulsory to have a so-called break tank, or storage tank, between the actual water supply and the manufacturing plant. Such storage tanks are common foci of contamination, often in the form of adhered biofilm on the tank walls and in associated pipework (Figure 4). 

Domingue, P.A., Sadhu, K., Costerton, I.W., et al. (1991) The human vagina normal flora considered as an in situ tissue-associated, adherent biofilm. Genitourin Med 67, 226-231. 

Microbial cells transported with the stream of fluid above the surface interact with conditioning films. Immediately after attachment, microorganisms initiate production of slimy adhesive substances, predominantly exopolysaccharides (EPS) that assist the formation of microcolonies and microbial films. EPS create bridges for microbial cells to the substratum and permit negatively charged bacteria to adhere to both negatively and positively charged surfaces. EPS may also control interfacial chemistry at the mineral/biofilm interface. 

Microsensors have been used to develop profiles in mixed species biofilms. Figure 10 shows concentration profiles of sulfide, oxygen, and pH in a biofilm accumulated on the surface of a mild steel corrosion coupon. The concentration of sulfide is highest near the metal surface, where iron sulfide forms quickly and covers the steel surface if both ferrous and sulfide ions are available. At low ferrous ion concentrations, adherent and temporarily protective films of iron sulfides are formed on the steel surface, with a consequent reduction in corrosion rate. High rates of SRB-induced corrosion of mild steel are maintained only in high concentrations of ferrous ion. 

Biofilms adhere to surfaces, hence in nearly all systems of interest, whether a medical device or geological media, transport of mass from bulk fluid to the biofilm-fluid interface is impacted by the velocity field [24, 25]. Coupling of the velocity field to mass transport is a fundamental aspect of mass conservation [2]. The concentration of a species c(r,t) satisfies the advection diffusion equation... 

Lower chemical reactivity with non-target molecules is useful for another performance-related reason. Microorganisms prefer the protection and luxuriant environment in biofilms (the adherent microbial communities that cause detrimental surface-fouling effects in water cooling systems). Most (>99%) of the viable microorganisms in industrial systems are found in biofilms, not floating around freely in the bulk recirculating water. Compared to unstabilized chlorine or bromine, STABREX more effectively removes and disinfects biofilms as shown in Table 6. 

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. 

U. linza spores adhere more strongly to SAMs of decreasing hydrophobicity (Finlay et al. 2002). Although settling preferentially on surfaces that provide the weakest attachment appears quite maladaptive, in nature an algal spore would virtually always be settling on a biofilm-coated surface (Callow and Callow 2006) rather than a clean surface such as those presented by SAMs. Presumably, in the microenvironments within a biofilm, selective settlement on relatively hydrophobic surfaces is adaptive, but this remains to be demonstrated experimentally. 

Yeast flocculation mechanism can be described as a phenomenon of adhesion to certain surfaces. The ability to adhere to surfaces and to form biofilm is the basis of the pathogenicity of Candida species. Pathogens adhere to mucous membranes and wounds, they stick to medical instruments and prosthesis, and thus contaminate surfaces in food processing facilities. The high mortality rate in disseminated fungal infections caused an increase in the amount of research on the molecular basis of the adhesive phenomena in Candida. This research discovered a considerable overlap in the molecular regulation of all forms of adhesive behavior. ... 

Biofouling involves the formation of biofilm, whereby hydrated algal- or bacterial-based slimes adhere to water-wetted cooling system surfaces and often contain scales, corrosion products, or other debris embedded within a polysaccharide matrix. The role of biofilms in reducing cooling system efficiency and life span is still imperfectly understood. 

Dispersant(s) or antifoulant(s) (sludge fluidizers, biodispersants, or mud treatments) to limit the physical adherence of insoluble salts, corrosion products, oils, fats, process contaminants, biofilms, and biomass onto heat-transfer and other water-wetted surfaces... 

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