Facultative anaerobes

Lactic Acid B cteri. The lactic acid bacteria are ubiquitous in nature from plant surfaces to gastrointestinal tracts of many animals. These gram-positive facultative anaerobes convert carbohydrates (qv) to lactic acid and are used extensively in the food industry, for example, for the production of yogurt, cheese, sour dough bread, etc. The sour aromatic flavor imparted upon fermentation appears to be a desirable food trait. In addition, certain species produce a variety of antibiotics. 

Free-living bacteria are, however, used as the source of the enzyme nitrogenase, responsible for N2 fixation (1,4,26,80), for research purposes because these ate easier to culture. The enzyme is virtually identical to that from the agriculturally important thizobia. These free-living N2-fixets can be simply classified into aerobes, anaerobes, facultative anaerobes, photosynthetic bacteria, and cyanobacteria. 

Facultative anaerobe A bacterium capable of growing under aerobic conditions or anaerobic conditions in the presence of an inorganic ion ie. SO4, NO3. 

Hydrolysis The process in which carbohydrates and starches are simplified into organic soluble organics, usually by facultative anaerobes. 

Studies on 4-hydroxybenzoate decarboxylase and 3,4-hydroxybenzoate decarboxylase have been restricted to obligate anaerobic bacteria, C. hydroxy-benzoicum Aside from the obligate anaerobic microorganism, C. hydroxy-benzoicum, very recently facultative anaerobic bacteria, Enterobacter cloacae strains exhibiting high 4-hydroxybenzoate decarboxylase or... 

The occurrence of 4-hydroxybenzoate decarboxylase was also found in facultative anaerobic bacteria, E. cloacae P240, and the enzyme was purified and characterized. The activity of the cell-free extract of E. cloacae P240 was determined to be 13.7 ijumol min (mg protein) at 30°C, which was much higher than... 

The occurrence of 3,4-dihydroxybenzoate decarboxylase was also found widely in facultative anaerobes. Among them, Enterobacter cloacae P241 showed the highest activity of 3,4-hydroxybenzoate decarboxylase, and the activity of the cell-free extract of E. cloacae P241 was determined to be 0.629 p.mol min (mg protein) at 30°C, which was more than that of C. hydroxybenzoicum, 0.11 (xmol min mg protein)" at 25°C. The E. cloacae P241 enzyme has a molecular mass of 334 kDa and consists of six identical 50 kDa subunits. The value for 3,4-dihydroxybenzoate was 177 p.M. The enzyme is also characteristic of its narrow substrate specificity and does not act on 4-hydroxybenzoate and other benzoate derivatives. The properties of E. cloacae P241 3,4-hydroxybenzoate decarboxylase were similar to those of C. hydroxybenzoicum in optimum temperature and pH, oxygen sensitivity, and substrate specificity. 

Figure 17. EIS Bode plot for epoxy coating over zinc-primed steel exposed for 2 months to uninoculated medium (curve 1) and six mixed cultures of facultative anaerobes (curves 2-7). (Reprinted from Ref 35 with permission from NACE International.)...

The genus Staphylococcus is traditionally associated with disease in humans. The demonstration (Monna et al. 1993) that a strain of Staphylococcus auriculans—isolated by enrichment with dibenzofuran and with no obvions clinical association—could degrade this substrate and carry out limited biotransformation of hnorene and dibenzo[l,4]dioxin serves to illustrate the unsuspected metabolic potential of facultatively anaerobic Gram-positive organisms. 

Jagnow G, K Haider, P-C Ellwardt (1977) Anaerobic dechlorination and degradation of hexachlorocyclo-hexane by anaerobic and facultatively anaerobic bacteria. Arch Microbiol 115 285-292. 

Sanford RA, JR Cole, JM Tiedje (2002) Characterization and description of Anaeromyxobacter dehalogenans gen. nov., sp. nov., an aryl-respiring facultative anaerobic myxobacterium. Appl Environ Microbiol 68 893-900. 

Francis CA, AY Obraztsova, BM Tebo (2000) Dissimilatory metal reduction by the facultative anaerobe Pantoea agglomerans. Appl Environ Microbiol 66 543-548. 

Decarboxylation of aromatic carboxylic acids has been encountered extensively in facultatively anaerobic Enterobacteriaceae. For example, 4-hydroxycinnamic acid is... 

A facultatively anaerobic organism designated Anaeromyxobacter dehalogenans (Sanford et al. 2002) was capable of dechlorinating ortho-chlorinated phenols using acetate as electron donor—2-chlorophenol was reduced to phenol and 2,6-dichlorophenol to 2-chloro-phenol (Cole et al. 1994). A strain of Desulfovibrio dechloracetivorans was also able to couple the dechlorination of ortho-substituted chlorophenols to the oxidation of acetate, fumarate, lactate, and propionate (Sun et al. 2000). 

Many contaminants contain nitrogen, phosphorus, or sulfur, and degradative organisms may utilize one or more of these leaving the major part of the substrate intact. This is particularly important for munitions-related compounds with a high N/C ratio, when the addition of carbon sources may lead to the favorable development of anaerobic or facultatively anaerobic microorganisms. 

At many sites, the subsurface environment will be anoxic or even anaerobic due to the activity of aerobic and facultatively anaerobic bacteria in the surface layers of the soil. It is therefore essential to take into consideration the extent to which anaerobic degradation may be expected to be significant. Reactions may take place under sulfidogenic or methanogenic conditions, and the occurrence of sulfate at sites containing building material waste and the metabolic versatility of sulfate-reducing bacteria makes them particularly attractive. 

Facultative anaerobe An organism that makes adenosine triphosphate by aerobic respiration if oxygen is present, but switches to fermentation under anaerobic conditions. 

The most critical issue to be investigated during the initial biofeasibility study is the determination of which metabolic mode—aerobic or anaerobic—is more appropriate for the specific contaminants. As shown in Table 14.5, the redox potential is closely related to the metabolic mode, and careful control of this parameter is required to maintain the optimum metabolic mode during bioremediation. A general rule is that the redox potential should be above 50 mV to maintain the activity of aerobic and facultative anaerobic microorganisms and below that value for strictly anaerobic m icroorganisms.12... 

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