Sessile bacteria

This process reduces the amount of control biocide employed in the control of contamination of oil production system waters by sessile bacteria. The biocide may be applied at intervals of 2 to 15 days. The duration of biocide application is preferably from 4 to 8 hours [1244]. 

This is a general name for a wide variety of corrosion processes that may be actively or passively influenced, or induced, by an even wider variety of microbiological organisms. The electrochemical reactions that occur always result in metal wastage, as with all other forms of corrosion the most active biocorrosion processes primarily involve sessile bacteria rather than planktonic bacteria, algae, or fungi. 

Matrices are primarily composed of polysaccharide slimes exuded by immobilized sessile bacteria. Planktonic organisms that become trapped can adapt to the new environment within minutes, and produce copious amounts of adherent and protective slime. 

Due to the reduced contact with the greater, external, aqueous environment, sessile bacteria are different from their planktonic cousins and react differently to changes within cooling systems. 

Gluteraldehyde + 10% block copolymer (BCP), a nonionic biodispersant. Dose at 40 to 50 ppm. Effective as a slime penetrant, sessile bacteria biocide, and biofilm remover. Not particularly suitable with high levels of ammonia or primary amine. 

Microbiological growth inc. planktonic sessile bacteria. Andformation of biofilms, slimes biomass... 

Geesey, G. G., R. Mutch, J. W. Costerton, and R. B. Green. 1978. Sessile bacteria An important component of the microbial population in small mountain streams. Limnology and Oceanography 23 1214-1223. 

One immediate result of such classification of bacterial states according to availability of nutrients is that, as in almost all experiments that are being carried out under laboratory conditions, the bacteria have all the required nutrients around them, and they may be inclined to prefer planktonic growth over sessile conditions, whereas a great majority of MIC problems come from sessile bacteria, not planktonic ones. This can call into question the reliability of such experiments, especially if one bears in mind the direct relationship between corrosion rate changes and sessile microorganism growth. ... 

The complexity of confusions about MIC does not end with the various ways of naming it or mixing it up with other corrosion phenomena while it has been stated that there is unequivocal evidence that the observable physical or biochemical characteristics of sessile bacteria are profoundly different from those of their planktonic cousins, it has also been reported that, for example, only 1% of Pseudomonas aeruginosa genes have revealed differential expression in planktonic and biofilm cells. 

There are very interesting features of the sessile bacteria that could be related to corrosion. Some of these interesting points are as follows ... 

It can be inferred, then, that sessile bacteria are not simply the planktonic bacteria joining the flock of the surface-attached bacteria. The sessile bacteria could by themselves be very complicated, and for sure, their impact on corrosion is a matter that will require more research. However, in addition to the possible effects that sessile bacteria (or, in fact, biofilms) can have on corrosion, one important matter about them is that when biofilms are formed, not only the genetic and... 

Resistance of the sessile bacteria (and thus, biofilms) to biocides is a known factJ - There are three mechanisms that have been proposed to explain this behavior of biofilms ... 

Szomolay et have developed a model to describe the interaction between biofilm thickness and biocides. They have postulated that in addition to the known mechanisms mentioned above (mechanisms 1, 2, and 3), some of the bacteria in a biofllm seem to be able to sense the biocidal material and actively respond to it. In this model, it is proposed that there is a relationship between the thickness of the biofilms and the activity of the biocide for the sessile bacteria. Put in simple words, the thicker the biofilm becomes, the more the bacteria learn to resist it. 

In fact, it is suggested that the indirect mechanism itself comprises two submechanisms the contact mechanism and the noncontact mechanism. While the contact indirect mechanism still takes into consideration the sessile bacteria and biofilm formation and their role in launching the electrochemical processes that will result in the dissolution of the sulfide mineral, the contact indirect mechanism describes the ferrous-ferric cycle by the oxidizing effect of the planktonic bacteria. A brief review of these submechanisms has been given elsewhere. ... 

A natural biocide, effective as a detachment agent against sessile bacteria on stainless steel surfaces... 

As the pit grows, what fills the headspace of the pit can be both biological and nonbiologi-cal matter (from sessile bacteria to corrosion products). The model assumes that all these fillers have similar sulfate diffusivities as fhe SRB biofilm. 

Viera, M. R., Guiamet, P. S., de Mele, M. F. L. and Videla H. A., 1999a. Use of dissolved ozone for controlling planktonic and sessile bacteria in industrial cooling systems. International Biodeterioration and Biodegradation 44, 201-207. 

Sessile bacteria are measured either by analysing deposits taken from the machine, or by using a fouling monitor, or following the rate and nature of deposition on a reference surface in the machine using either a microscope to see individual sessile cells of enumerating some of the microbes present by plating the actual deposit. 

Stage 3 Different species of sessile bacteria replicate on the metal surface. 

Stage 6 The exposed areas of the surface are recolonised by planktonic bacteria or sessile bacteria adjacent to the exposed areas. 

One of the possible effects of sessile bacteria on planktonic bacteria is actually addressing the effect that biofilms can have on accelerating biocorrosion. This discussed was in Chapter 4 and will not be repeated here. 

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