Bacterial Growths

There are a number of chemical and physical requirements for bacterial growth, such as carbon and nitrogen sources, pH, and temperature (see Chapter 1). Some antibiotic assay organisms, such as Bacillus subtilis and Escherichia coli, grow on simple media, others, such as the lactobacilli used for vitamin assay, need an enriched medium containing a wide range of nutritional supplements. Many media are commercially available in the dehydrated form from various suppliers. 

To arrive at testable predictions, we go one step further by taking the steady state of constant intracellular ATP concentration, a condition that is reached very quickly [22,50]. This steady-state condition allows us to eliminate one of the forces, prefer- 

Both equations are equally valid. It turns out, however, that the practical applicability differs according to the experimental conditions. 

In the simplest case, where catabolism and anabolism follow completely independent routes, we can define either catabolism or anabolism as limiting . When one of the catabolic substrates is limiting, the free energy of anabolism is effectively constant (in biochemical terms substrates for anabolism are always saturating ) 

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In addition to their antiknock properties, organic lead compounds possess bactericidal properties and motor fuels with lead are known to inhibit bacterial growth during storage in contact with water. With the disappearance of lead-based compounds, it is necessary to incorporate biocides from the cyclic imine family, (piperidine, pyrrolidine, hexamethyleneimine), alkylpropylene diamines or imidazolines (Figure 9.2). 

Bacteria require p-aminobenzoic acid to biosyn thesize folic acid a growth factor Structurally sul fanilamide resembles p-aminobenzoic acid and is mistaken for it by the bacteria Folic acid biosynthesis IS inhibited and bacterial growth is slowed suffi ciently to allow the body s natural defenses to effect a cure Because animals do not biosynthesize folic acid but obtain it in their food sulfanilamide halts the growth of bacteria without harm to the host... 

Microbial-enhanced oil recovery involves injection of carefully chosen microbes. Subsequent injection of a nutrient is sometimes employed to promote bacterial growth. Molasses is the nutrient of choice owing to its low (ca 100/t) cost. The main nutrient source for the microbes is often the cmde oil in the reservoir. A rapidly growing microbe population can reduce the permeabiHty of thief zones improving volumetric sweep efficiency. Microbes, particularly species of Clostridium and Bacillus, have also been used to produce surfactants, alcohols, solvents, and gases in situ (270). These chemicals improve waterflood oil displacement efficiency (see also Bioremediation (Supplement)). 

Some related antibacteiials are also included with the sulfonamides. The azo dye, Piontosil (3) is metabolized to sulfanilamide in and was the piogenitoi of the sulfa dmgs. Also, the antibacteiial sulfones, eg, dapsone (4), are believed to act in a similai fashion on enzymes involved with synthesis of fohc acid, leading to bacterial growth inhibition. 

The mode of action of the naphthoquinoid ansamacroHdes was estabHshed through studies using the tifamycins and streptovaricins (84,141,257,258). The ansamacroHdes inhibit bacterial growth by inhibiting RNA synthesis. This is accompHshed by forming a tight complex with DNA-dependent RNA polymerase. This complex is between the ansamacroHde and the P-unit of RNA polymerase. The formation of the complex inhibits the initation step of RNA synthesis (259,260). The ansamacroHdes form no such complex with mammalian RNA polymerase and thus have low mammalian toxicity. 

Salt preserves foods by providing a hostile environment for certain microorganisms. Within foods, salt brine dehydrates bacterial cells, alters osmotic pressure, and inhibits bacterial growth and subsequent spoilage. Dry salt and salt brine are used in several types of curing processes. Pickles are preserved in strong brine before final processing. 

Submerged culture oxidizers can also be operated on a continuous basis. Continuous monitoring of ethanol and acetic acid concentrations, temperature, and aeration rates permit control of feed and withdrawal streams. Optimum production, however, is achieved by semicontinuous operation because the composition of vinegar desired in the withdrawal stream is so low in ethanol that vigorous bacterial growth is impeded. Bacterial... 

During the 1 agering period, temperatures are generally so low that bacterial growth is insignificant. Bacteria carried through the filters have Httle chance to develop if the beer is pasteurized siace this iaactivates most microorganisms. 

The converted mash is pumped to a clean sterilised fermentor and the yeast inoculum is added. The set temperature range for whiskey fermentation of 72 hours is usually 17—21°C. At the beginning, the mash converted composition is approximately 80% sugars, mainly maltose and some (<1%) dextrose (primary conversion). The pH is adjusted to reduce initial bacterial growth. Grain neutral spidts are usually set at 27—29°C to expedite fermentation. Temperatures above 35°C inhibit yeast reproduction and promote rapid bacterial growth. Above 40°C actual yeast kill occurs. 

Phenol Coefficient Test. The first important attempt at standardizing testing methods was known as the phenol coefficient test (96). It has been modified several times, and is an official AO AC screening test recognized by EPA and PDA. The phenol coefficient test compares the activity of disinfectants to that of phenol, under specific conditions, to give a number that measures the activity of the chemical tested with respect to that of phenol, ie, the phenol coefficient. The AO AC method employs visual examination of bacterial growth in a nutrient medium. The Kelsey-Sykes test (1969) is a modified method popular in British circles. 

Modify the environment After cleaning and disinfecting an area that is contaminated by fungal or bacterial growth, control humidity to make conditions inhospitable for regrowth. 

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