Effect of Manual Brush Cleaning on Biomass and Community Structure of Microfouling Film Formed on Aluminum and Titanium Surfaces Exposed to Rapidly Flowing Seawater

Abstract

Metals exposed to rapidly flowing seawater are fouled by microbes that increase heat transfer resistance. In this study, results of biochemical test methods quantitatively relating the biomass and community structure of the microfouling film on aluminum and titanium to heat transfer resistance across the metal surface during three cycles of free fouling and manual brushing showed that cleaning accelerates the rate of fouling measured as the loss of heat transfer efficiency and as microfouling film biomass. The results also showed that the rate of fouling, measured as an increase in heat transfer resistance, is faster on titanium than on aluminum but that the titanium surface is more readily cleaned. In three cycles of free fouling and cleaning with a stiff-bristle nylon brush, the free-fouling communities reforming on aluminum became enriched in bacteria containing short-branched fatty acids as the cycling progressed. The free-fouling community on titanium revealed an increasingly diverse morphology under scanning electron microscopy that was enriched in a portion of the microeucaryotes. Brushing removed most of the biomass, but left a residual community that was relatively enriched in a portion of the bacterial assembly containing cyclopropane fatty acids on aluminum and in a more diverse community on the titanium surface. The residual communities left after cleaning of titanium revealed an increase in bacteria with short-branched fatty acids and in microeucaryotes as cleaning continued. No significant changes occurred in the residual microbial community structure left on aluminum with cleaning; it was, again, less diverse than that remaining on titanium. The residual communities secreted a twofold-larger amount of extracellular polymer, measured as the ratio of total organic carbon to lipid phosphate, than did the free-fouling community on both surfaces.

Factors Regulating Microbial Biofilm Development in a System with Slowly Flowing Seawater

“…Increasing flow increases the shear forces on a biofilm and the velocity of the transport mechanisms to and from a biofilm. Together with relatively high temperatures (-25°C), this could explain why OTEC research workers report more compact, filamentous (1,13) and productive (pO-50 = 4 to 16 pLg [dry weight] cm-2 day-', depending on tube material [10]) biofilms as compared with what is reported here. An additional reason for the difference may be the difference in the material and the structure of the solid surfaces (metal versus glass).…”

Estimations of Uronic Acids as Quantitative Measures of Extracellular and Cell Wall Polysaccharide Polymers from Environmental Samples

“…Indirect effects of these polymers include the stabilization of sediments and soils by the presence of invertebrate feeding tubes and microbial extracellular polysaccharide polymers (19,20,36,49). Recent evidence has indicated that microbially produced extracellu-lar polymers may be particularly important in heat transfer resistance by the microfouling community that is formed when metal surfaces are exposed to rapidly flowing seawater (33,34).…”

“…Samples of titanium (commercial grade) and 5052 aluminum pipes were exposed to seawater that was flowing at 1.85 m/s at the Naval Coastal Systems Center, Panama City, Fla. The pipe samples were removed from the system, drained, frozen, and returned to the laboratory; the lipids were extracted; and the pipes were allowed to dry (33). The extracellular polymer was recovered by the exposure of the insides of the pipes to a suspension of 25% (wtl vol) acid-washed, 00-mesh, silicate rock chips in distilled water containing 10o chloroform in a specially constructed shaker that subjected the inside surfaces to the abrading action of the chips.…”

“…Studies of heat transfer resistance across metal pipes exposed to rapidly flowing seawater have shown that the extracellular polymer films secreted by the microfouling community are of primary importance (32,33). The polymer re- (Table 2).…”

Environmental effects testing with quantitative microbial analysis: Chemical signatures correlated with in situ biofilm analysis by FT/IR

“…Uncontaminated subsurface aquifer sediments contain microbiota with very high levels of extracellular polysaccharides indicating poor nutrient conditions ). The microfouling community formed on metal surfaces exposed to rapidly flowing seawater shows a rapid accumulation of uronic acid containing extracellular glycocalyx as a response to mechanical or chemical countermeasures (Nickels et al 1981a;1981c;White and Benson 1984). Preliminary evidence indicates that these polymers have a role in increasing marine sediment stability (Nowell et al 1985).…”