Anaerobic bacterial activity

In the presence of hydrogen sulfide produced by anaerobic bacterial activity, particularly sulfate reducers, conditions are created whereby sulfides of copper and zinc could be formed. The partition of these metals between the sulfide phase and the organic phase depends on the relation between the stability constants of the complexes and the solubility product of the sulfides of these metals. Elements with small solubility products of their sulfides and low stability constants of their chelates would be expected to go into the sulfide phase when hydrogen sulfide is present. Copper is typical of such elements. Chalcocite has a solubility product of about 10" ° and covellite about 10"44, whereas the most stable chelates of copper have stability constants of about 10" Consequently, copper could be expected to be accumulated as the sulfide. Zinc sulfide has a much larger solubility product however, the stability of its chelates is lower. From the fact that zinc appears to be completely associated with the inorganic fraction of coal, it can be assumed that the relation between the solubility product of any of its sulfides and its chelates favors formation of the sulfide. Iron could be expected to follow a similar pattern. 

Among contaminants one of the most objectionable is oil, especially in systems where water is strongly heated. A relatively small amount of oil on a heating surface can produce very rapid failures. An indirect effect of oil, or other contaminants which form films on the water surface, is that the film isolates the water from air so that in polluted water anaerobic conditions may develop with the encouragement of objectionable bacterial activity. 

Bacterial activity often plays a major part in determining the corrosion of buried steel. This is particularly so in waterlogged clays and similar soils, where no atmospheric oxygen is present as such. If these soils contain sulphates, e.g. gypsum and the necessary traces of nutrients, corrosion can occur under anaerobic conditions in the presence of sulphate-reducing bacteria. One of the final products is iron sulphide, and the presence of this is characteristic of attack by sulphate-reducing bacteria, which are frequently present (see Section 2.6). 

The presence of HjS (from bacterial activity in anaerobic saline mud, for example) can result in a significant decrease (16%) in capacity and loss of operating potential for Al-Zn-ln anodes... 

Two studies compared the effect of rifaximin to that of neomycin and/or of rifampicin [72, 73] on the fecal flora in rats. In the first study [72] the antibiotic (1, 10, 30 and 100 mg/kg orally for 7 days) did inhibit both aerobic (especially coliforms and cocci) and anaerobic bacterial growth. Its activity was similar to that of neomycin and stronger than that of rifampicin. In the second investigation [73] the antibiotic effect on aerobic microorganisms was specifically investigated. Oral rifaximin treatment (50 mg/kg for 3 days) caused a marked reduction in the number of total aerobic bacteria and salmonellae, while neomycin led only to a decrease in salmonella counts, but did not cause statistically significant changes in the total aerobic bacterial population. 

Welling GW, Meijer-Severs GJ, Helmus G, van Santen E, Tonk RH, de Vries-Hospers HG, van der Waaij D The effect of ceftriaxone on the anaerobic bacterial flora and the bacterial enzymatic activity in the intestinal tract. Infection 1991 19 313-316. 

Anaerobic bacterial reactions are much slower and produce only a fraction of the energy produced by aerobic activity. Alternate electron acceptors are generally consumed in a stepwise process ... 

Lactate is an important marker compound in many biomedical, food and beverage applications. Blood lactate is monitored in exercise control and sports medicine, and D-lactate is an indicator of bacterial activity in wine fermentation [59,60,63]. Lactate produced from anaerobic respiration of cattle muscle subsequent to slaughter has been investigated as an indicator of meat freshness [62],... 

Arnosti, C., and D. J. Repeta. 1994a. Extracellular enzyme activity in anaerobic bacterial cultures Evidence of pullulanase activity among mesophilic marine bacteria. Applied and Environmental Microbiology 60 840-846. 

The presence of bacterial activity can be qualitatively estabfished by placing a few drops of hydrochloric acid on the corrosion products. The evolution of H2S indicates the existence of anaerobic bacteriological activity. The bacteriological existence is also established by measuring the redox potential. This can be done by placing a redox probe into freshly dug soil at the pipeline depth. The potential is measured between a clean platinum surface and a saturated calomel reference electrode [49—53]. The redox potential measurement data and the tentative anticipated bacteriological activity are shown in Table 15.4. 

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