Bacillus growth rate

The CAST uses Bacillus megatherium and a 16-24 h incubation at 44-45 C, whereas STOP employs Bacillus subtilis and a 16-24 h incubation at 27-29 C. A zone of inhibition around the swab suggests the presence of a microbial inhibitor in the sample. In the US, bob veal calf carcasses are condemned on the basis of a positive CAST without further confirmation. For FAST, the organism and temperature are the same as those for the CAST, but the CAST medium is supplemented with dextrose and bromocresol purple. The faster growth rate of bacteria with FAST, allows reduction of minimum incubation from 16 to 6h. 

The stationary phase classically represents the stage at which the rate of cell division equals the rate of cell death, so the number of viable cells remains constant. This phase usually occurs when the cell concentration reaches a sufficient size that some property of the environment restricts growth rate, often a nutrient where phytoplankton are concerned. Physiological changes can occur, including adaptations that promote cell survival through periods of limited growth. Some bacteria (e.g. species of Bacillus and Clostridium) form endospores, which represent a dormant state that is resistant towards levels of desiccation, heat, chemical or radiation exposure that would prove lethal to the non-endospore forms. 

Fig. 2. Secretion of Bacillus subtilis protein into the medium with different concentration of casamino acids. Cultivation conditions and samples were identical as described in Figure 1. The duration of the experiment was 210 min. Growth rate was monitored from absorbance values obtained at 650 nm, taken at 30 min intervals, o, 0.2 mg casamino acids/ml, , 2 mg casamino acids/ml.

Fig. 2.36. Growth rate and temperature for 1) psy-chrophilic (Vibrio AF-1 2) mesophilic (E. coli K-12) and 3) thermophilic (Bacillus cereus) microorganisms (according to Herbert, 1989)...

Recently, the control of the increase in growth rate following amino acid upshift was studied in Bacillus subtilis. The GTP pools were manipulated by using mycophenolic acid, an inhibitor of guanine nucleotide biosynthesis, and by guanosine supplementation. It was found that an increase in GTP levels was required to obtain the growth rate increase on amino acid upshift (92). 

Further efficient fermentative methods for manufacture of riboflavin have been patented one is culturing C. famata by restricting the carbon source uptake rate, thereby restricting growth in a linear manner by restriction of a micronutrient. By this method, productivity was increased to >0.17 g riboflavin/L/h (63). The other method, using Bacillus subtilis AJ 12644 low in guanosine monophosphate hydrolase activity, yielded cmde riboflavin 0.9 g/ L/3 days, when cultured in a medium including soy protein, salts, and amino acids (64). 

Most aiititubercular drag s are bacteriostatic (slow or retard the growth of bacteria) against the M. tuberculosis bacillus. These dm usually act to inhibit bacterial cell wall synthesis, which slows the multiplication rate of the bacteria. Only isoniazid is bactericidal, with rifampin and streptomycin having some bactericidal activity. 

Fig. 33.1. Results of a batch experiment (symbols) by Blum et al. (1998) in which Bacillus arsenicoselenatis grows on lactate, using arsenate [As(V)] as an electron acceptor. Solid lines show results of integrating a kinetic rate model describing microbial respiration and growth.

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