Bacteria bacterial strain

The Ames test involves the reversion from a his— to his+ phenotype in any one of multiple bacterial strains (usually five strains are tested simultaneously). If the addition of test compound to a his— strain of bacteria allows them to grow on histidine deficient media, the obvious conclusion is compound-induced mutagenesis and a high potential hazard for the compound being carcinogenic. This test can also be conducted in the presence or absence of metabolic activation, in order to provide more information on potential risks (i.e., the parent compound may not be mutagenic, but the primary metabolite may present a safety risk). In practice, a positive Ames test almost always leads to discontinuing work on a compound of interest, and so these data are always collected prior to nomination of a compound for development. 

The direct whole-cell method of Holland et al. was extremely rapid, even in comparison to Lubman s MALDI analysis of fractions collected after bacterial sonnication. With the whole-cell approach bacteria were simply sampled from colonies on an agar plate, mixed with the matrix, air-dried, and introduced in batches into the mass spectrometer for analysis. In all of the spectra obtained in these and later experiments, each bacterial strain showed a few characteristic high-mass ions that were attributed to bacterial proteins. Studies demonstrating the whole cell methodology for strain-level differentiation were reported independently by Claydon et al. at almost the same time.18 Shortly thereafter a third study on whole-cell MALDI included bacteria from pathogenic and nonpathogenic strains appeared.19... 

Encouraged by this spectral reproducibility, we focused our efforts on the particularly challenging problem of distinguishing bacterial strains by MALDI MS. We developed a modified correlation approach22 that relies on two fundamental qualities of bacterial mass spectra. First, because different bacterial strains of the same species have substantial, if not complete, genetic overlap, most of the protein masses observed with two different strains will be identical. This feature limits the value of the biomarker approach that is commonly used to differentiate bacteria species. Second, as just noted, closely controlled sample preparation and mass analysis procedures can result in highly reproducible results.22 The modified correlation approach takes advantage of subtle, yet reproducible, differences in mass spectra obtained from dif-... 

While this chapter has described two examples of our efforts in bacterial strain identification, a number of other groups have contributed to this research area. It remains to be seen whether mathematical algorithms such as the modified correlation approach described herein are always more effective for strain assignments than the simple use of distinctive biomarker peaks. Nilsson reported MALDI mass spectra of Helicobacter pylori with three different matrices and solvent conditions.59 She showed that some strains of this bacteria yield rather similar mass spectra while others are quite different. Nevertheless, each strain appears to exhibit some unique peaks that might be used for distinguishing strains. 

Mid-IR spectroscopy, alongside gravimetric and molecular weight determinations, has also been used to analyse the biodegradation by a thermophilic bacterium (isolated from soil) of an LDPE film [44], The mid-IR studies were undertaken using the ATR sampling technique on control samples, samples that had been UV irradiated, and samples that had been UV irradiated then incubated with bacteria. The study showed that the particular bacterial strain was capable of utilising standard and photo-oxidised polyethylene as the sole carbon source. 

At least 53 PHA synthases have meanwhile been cloned from 42 different bacterial strains, and the nucleotide sequences of 38 different PHA synthases from 31 different bacteria have been obtained (Table 1, Fig. 2). That the number of sequenced PHA synthases exceeds the number of bacteria from which they have been cloned is due to the occurrence of two or even more PHA synthase genes in some bacteria. The organization of PHA synthase genes and other genes of... 

Various other bacterial strains and processes have been studied by academic groups for the production of poly(3HB) or poly(3HB-co-3HV), several of which are presented here. Some methylotrophic and methanotrophic bacteria are interesting for poly(3HB) production purposes. Methanol is an inexpensive substrate and there is considerable experience in methanol fermentation techno-... 

A microbial contacting process for the oxidation of H2S was disclosed [22], in which a chemoautotrophic bacterium T. thiooxidants or T. ferroxidans) is used to remove sulfides from gaseous streams, at aerobic conditions and low pH. The low pH is preferred since the optimum pH for growth of the bacteria is below 4.0. and for the elimination of undesired contaminant bacterial strains. A contactor is employed, the flow of the sulfur-containing stream is contacted counter-currently with the biocatalytic aqueous solution. The sulfate is recovered from the aqueous solution, which contains the biocatalyst, as well. 

Some heavy metal-tolerant bacterial strains and their sorption capacities for Cu and Cd are listed in Table 1. These bacteria show great potential for remediating soils that are contaminated with toxic metals. Our pot culture experiments showed that the growth of tobacco plants in a Cd-polluted Yellow Brown Soil (Alfisol) was significantly promoted by inoculating the soil with P. Putida in comparison with the non-inoculated soil (Fig. 2). 

Identification of azo dye degrading bacterial strains for use in bioaugmentation typically involves a stepwise process to isolate potential strains and screen them for their ability to degrade different dyes. A number of strategies have been devised to isolate such bacteria to achieve consistent and reproducible results in biotreatment systems (Fig. 2). Specific methods that have been employed for the isolation of microbial strains capable of degrading azo dyes are summarized in Table 2. 

Resmi et al. [59] used laterite stones for the immobilization of Pseudomonas putida (MTCC 1194). The amount of bacterial biomass attached to the support was 8.64 g/100 g of stones on dry weight basis. Packed bed reactor was used for treating mixture of seven azo dyes. With the help of immobilized bacterial strain, dye mixture was degraded to nontoxic smaller molecules. It was reported that even after 2 months, bacteria-coated pebbles were stable and suitable for the aerobic degradation of azo dyes. With the help of TLC and HPLC, 61.7% degradation was reported at the concentration of 50 pg/mL of dye. 

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