Anaerobic cultural media

Media are classified in various ways they may be classified as aerobic and anaerobic culture media, on the basis of molecular oxygen and reducing substances in the media, or solid or liquid, based on the physical state. 

The methods required to create and maintain conditions that are suitable for growing anaerobic cultures are more difficult than those required for culturing aerobic cultures. Nonetheless, use of methods such as the serum bottle modification of the Hungate technique [24] is now routine in many laboratories. As discussed in the previous section, the formulation of the medium depends on whether the fiber or fabric is to serve as the sole source of carbon, nitrogen or sulfur. In addition, the formulation of the anaerobic culture medium depends upon which terminal electron acceptor is to be considered in the study. As shown in Table 1.2, the list of terminal electron acceptors includes Mn(IV), nitrate, Fe(III), and sulfate. In addition, bicarbonate (carbon dioxide) serves as the terminal electron acceptor for methanogenesis (equation 1.1). Supplementing the medium with an abundant supply of one of the terminal electron acceptors prescribes the microbial process that occurs in the cultures. Fermentation, in which some oxidized organic compound serves as the terminal electron acceptor, also occurs under anaerobic conditions. 

Shewanella J18 143 Remazol Black B, Acid Orange 7 Anaerobic cultures of Shewanella strain J18 143 rapidly removed color from the azo dye Remazol Black B in the growth medium to produce an absorbance at 597 nm of less than 1 in under 40 min [86]... 

Under anaerobic conditions, various pathways exist for pyravate metabolism which serve to re-oxidize the reduced hydrogen carriers formed during glycolysis. The ultimate acceptor builds up as a waste product in the culture medium. The end-products of the pathways are (1) CO, ATP, and acetate (2) COj and ethanol (3) and CO2 (4) COj and 2,3-butylene glycol (5) COj, Hj, acetone, ATP, and butanol (6) succinate and (7) lactate. The pathway that occurs depends on the microorganism cultivated and the culture. 

Fig. 16.33 Simultaneous (a) toluene conversion and (b) AQDS reduction by Amsterdam petroleum harbor sediment in anaerobic culture bottles containing bicarbonate-buffered basal medium, supplemented with 25 mM AQDS. The unsupplemented control was prepared in the same manner but without AQDS. The endogenous control (without toluene addition) contained the same amount of hexadecane (0.2% [vol/vol]) as that used for toluene addition. AQDS reduction was quantified spec-trophotometiicaUy as the increase in absorbance at 450 nm. Data are means and standard deviations for tiiphcate incubations in each treatment. Arrows indicate the addition of fresh medium containing AQDS and toluene in depleted bioassay mixtures. (Cervantes et al. 2001) Reprinted with permission. Copyright American Society for Microbiology...

Chaudhuri, B. K. Wiesmann, U. (1995). Enhanced anaerobic degradation of benzene by enrichment of mixed microbial culture and optimization of the culture medium. Applied Microbiology and Biotechnology, 43, 178-87. 

There are differences in the pathways of thiamin hiosynthesis between prokaryotes and eukaryotes, and also between organisms that are aerobes and facultative anaerobes. Some organisms are completely autotrophic for thiamin, whereas others require the presence of either preformed pyrimidine or thiazole in the culture medium, and indeed some require both. 

D-Galactanases have been reported to be produced by Bacillus subtilis, by a rumen anaerobic bacterium, by fungi, and by plants (see Table V). D-Galactanases are inductive, and those of microbial origin are usually produced extracellularly in response to the carbon source of the culture medium. 

Liquid samples can be analysed directly by the spread plate (A) or the pour plate method (B) but they can also be filtered to retain the micro-organism on a filter which is than placed on the culture medium (C). Suspensions need to be filtrated or centrifuged afterwards the filtrate or the filter can be analysed. Solids (e.g. food) must be minced before filtration. Incubation at a given temperature can be aerobic or anaerobic. The result of the counting will depend on the ability to isolate the target organisms with the best recovery rate. 

Demethylation of Free and Ester-linked Ferulic Acid by Sonicated Cellular Extracts of SR3. The O-demethylase activity of the SR3 strain was not excreted in the culture medium. To demethylate ferulic acid esterified to WEAX, which cannot penetrate the cells, a cell extract of SR3 strain was prepared by anaerobic sonication (MSON 05 Bio block, 20 Hz, 3 cycles of sonication of 2 min 2 s pulses separated by 2 s lag phase). The sonicated cellular extract of SR3 was tested in anaerobiose on free ferulic acid and esterified ferulic acid at 37 °C with a bacteria protein/ferulic acid ratio of 100 mg/ mol. Composition of reaction medium has been chosen in agreement with previous works on the demethylation of methoxylated phenolic compounds by other strains.15 20-22 In order to limit the viscosity of the medium, a 0.5% arabinoxylan concentration was used, corresponding to a 50 / M ferulic acid concentration. 

Secondly, we attempted to enrich the amounts of GABA in Chlorella cells. The glutamic acid-rich Chlorella cells produced 334 mg% of GABA in culture medium adjusted to pH 4.0 after 1 h-incubation at 38°C under anaerobic conditions. 

Inoculum was prepared by growing cells in 100-ml vials containing 45 ml anaerobic synthetic medium (BA medium) [13], amended with 1 g/1 yeast extract but without cystein. The medium was neutralized and flushed for 15 min with a mixture of N2/CO2 (4 1) to ensme anaerobic conditions before autoclaving at 140°C for 20 min. Prior to inoculation, the mediinn was reduced with a sterile anaerobic solution of sodium sulfide to a final concentration of 0.5 g/1. Xylose and vitamins were further added from filter-sterilized anaerobic solutions of D-xylose and vitamins DSMZ medium No 141 (German Collection of Microorganisms and Cell Cultures) to initial concentrations of 5 g/1 and 10 ml/1, respectively. The medium was inoculated with 10% (v/v) culture and incubated overnight at 70°C in the dark without shaking. 

In samples with hydrophobic compounds, enumeration of SRB and general anaerobic bacteria (GAnB) may be compromised because of the low solubilization of these compounds in the culture medium. The study of the influence of surfactants in the SRB and GAnB estimation in oil samples may become an alternative to improve the MPN method under these conditions. Surfactants are organic compounds that present both a hydrophobic part and a hydrophilic part in the same molecule. This hydrophilic part allows surlaclants to be soluble in water, whereas the hydrophobic part causes them to concentrate at interfaces [4]. 

The role of oxygen in eukaryotic DNA biosynthesis may indeed be a critical one. It has recently been shown that O2 is not only required for initial formation of tyrosyl radical but must be continously present to maintain the radical content and enzyme activity of mammalian ribonucleotide reductase In vivo studies with Ehrlich ascites cells also point to a tight link between oxygen and deoxyribonucleotide supply Anaerobic arrest of cells in G1 phase and block of DNA synthesis can be relieved by addition of deoxycytidine, but not cytidine, to the culture medium. ... 

Further observations on this effect by Wang et al. (16) have shown that cells taken from the culture medium anaerobically and diluted in anaerobic buffer exhibit a 100% efficiency of excitation transfer in the absence of dithionite. They also observed that the intensity of fluorescence from BChl d (measured at 760 nm) decreased under aerobic conditions. This suggests that aerobic conditions create quenchers within the chlorosome that compete with excitation transfer for BChl d excited states. Wang et al. (16) also found that oxidants other than O2, such as benzc uinone and Fe(CN)6 + TMPD, caused a similar decrease in the efficiency of excitation transfer, indicating that the critical factor is redox potential and not the presence of O2 per se. 

The viable cell count of bacterial cultures is determined by plating out suitable dilutions of culture on solid growth medium and counting the number of colonies formed after incubation. In addition to a correct supply of nutrients, bacterial G. depends on the pH, temperature and osmotic pressure of the culture medium, and on the degree of aeration (aerobes) or the completeness of anaerobiosis (anaerobes). 

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