Floating biofilms

Sampling procedures can also affect the type and frequency of microbial contaminants recovered from a contaminated fuel storage tank. The collection of samples, using a fuel sampler, provides data only on the planktonic population present in the tank water bottom and the fuel/water bottom interface where floating biofilm could be sampled. This sampling provides no information on the possible large sessile population attached to the walls of the tank. In many cases the actual level of contamination present is underestimated or misrepresented. 

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. 

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... 

Similar to the microbial biofilm preparations described above, free-floating, viable microbial mats are also successful in removal of metals from solution (Bender Phillips, 1994 Vatcharapi jarn, Graves Bender, 1994). Consisting primarily of algae, cyanobacteria and bacteria, microbial mats perform a number of activities which promote metal complexation and subsequent removal. The mat contains oxidizing and reducing zones that aid in the immobilization and precipitation of... 

Gradients of nutrients and oxygen in biofilms additionally promote high diversity, which may ultimately result in functional differences of the bacterial community in biofilms compared with free-floating bacteria. Additionally, increased species diversity may provide spatial and temporal niches not available within monocultures or may create microenvironments within the biofilm (Gieseke et al., 2001 Whiteley et al., 2001). These thoughts reinforce the need for community-level biofilm studies as opposed to monocultures. 

Biofilms, Microbiologists recognize two different populations of microorganisms. Free-floating (planktonic) populations are found in the bulk water. Attached (sessile) populations colonize surfaces. The same kinds of microorganisms can be found in either population, but the sessile population is responsible for biofouling. 

Chronic infections in contrast tend to be focal infections, limited in size, that wax and wane for long durations and are only partially destructive to tissues. The strategies of a single-cell, mobile, free-floating bacterium versus those of a community of bacteria encased in a self-secreted protective matrix (biofilm) are radically different and may one type of infections "chronic." Biofilm is intrinsically resistant to host immunity, antibiotics, and biocides, different treatment strategies will be required. Chronic infections such as chronic wounds, surgical-site infections, and infected implants will yield only to repetitive evaluation and multiple simultaneous therapies that require much persistence from the physician. 

The dissolved gas phase then has to dilfnse through the biofilm, and the reaction is allowed to occur. The biofilm is usually attached to the membrane rather than being allowed to float (Henstra et al., 2007). Additional problems are created because any by-products, which may be toxic if they are allowed to concentrate, have to leave the reactor through the same manner. In other words, microbial operation may have significant effects on the gas phase concentrations (gas-liquid mass transfer driving force), which could become an additional restriction on total gas-Uquid mass transfer (Kumar et al., 2008). 

Common types of plastics found as ocean debris are listed along with their densities in Table 10.1. Those denser than seawater (p 1.025 g/cm ) will sink and invariably end up in the marine sediment. The long-term fate of even the floating plastics, however, will be the same. A surface biofilm of bacteria and diatoms develops... 

The importance of biofilms in this process can not be overestimated. There are very good reasons to believe that bacteria are not free floating in a paint, but most of them are living in biofilms or are adhered to surfaces of the ingredients and the equipment. Biofilms in production equipment like tank surfaces, water pipes, on sealants, on filters are built easily and quickly within hours. They can not be removed by simple means but can cause consecutive and unpredictable introduction of locally high microbial counts and biological material in the paint. See also chapter 5.1. 

Fig. 2.3 Schematic representation of microbial community (biofilm) formation in Fukuyama kurozu fermentation. Koji mold, yeasts, and lactic acid bacteria are floating or sunk to form a biofllm at the bottom of the pot, and acetic acid bacteria form a biofllm on the surface of the fermented broth (Figure is revised from the original figure by Furukawa et al. 2013)...

Up till now most of the SECM experiments have been carried out in liquid or gel phases. Biofilms, life tissues, microorganisms however often are confined on solid surfaces or forming thin floating films on air/water interfaces. For SECM investigation of the behavior of these samples without causing major invasion the... 

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