The detection of Clostridium welchii in the differential reinforced clostridial medium technique

Design of mutualistic microbial consortia for stable conversion of carbon monoxide to value-added chemicals

Carbon monoxide (CO) is a promising carbon source for producing value-added biochemicals via microbial fermentation. However, its microbial conversion has been challenging because of difficulties in genetic engineering of CO-utilizing microorganisms and, more importantly, maintaining CO consumption which is negatively affected by the toxicity of CO and accumulated byproducts. To overcome these issues, we devised mutualistic microbial consortia, co-culturing Eubacterium limosum and genetically engineered Escherichia coli for the production of 3-hydroxypropionic acid (3-HP) and itaconic acid (ITA). During the co-culture, E. limosum assimilated CO and produced acetate, a toxic by-product, while E. coli utilized acetate as a sole carbon source. We found that this mutualistic interaction dramatically stabilized and improved CO consumption of E. limosum compared to monoculture. Consequently, the improved CO consumption allowed successful production of 3-HP and ITA from CO. This study is the first demonstration of value-added biochemical production from CO using a microbial consortium. Moreover, it suggests that synthetic mutualistic microbial consortium can serve as a powerful platform for the valorization of CO.

A new selective medium for the culture of clostridia from human faeces

A new selective medium, sulphite-polymixin-milk (SPM) agar, for the isolation of clostridia from faeces is described. This medium contains whole cow's milk, which favours the growth of clostridia over that of Bacteroides and Bifidobacterium spp., and only small amounts of colistin (10 micrograms/ml) for suppressing growth of coliforms. The alkaline end-products of clostridia give rise to yellow colonies on a red background which are easy to distinguish from the red colonies of other not completely inhibited bacteria. The medium is suitable for isolation of many clostridia species. Comparisons were made between SPM and several other media for recovery of clostridia. The detection limit on SPM agar was more than 10(3) below that on Reinforced Clostridia Agar (Oxoid CM101).

Comparison of media and methods for counting Clostridium perfringens in poultry meat and further-processed products

A Most Probable Number (MPN) method involving Differential Reinforced Clostridial Medium followed by streaking on Willis & Hobbs medium was compared with direct plating of samples on Tryptose-Sulphite-Cycloserine agar without egg yolk, and two forms of Oleandomycin-Polymyxin-Sulphadiazine-Perfringens agar, one being prepared from a commercial, dehydrated product. With skin samples taken from chicken carcasses at different stages of processing, the three direct plating media gave similar counts of Cl. perfringens whereas results obtained with the MPN method were consistently lower. Although counts of Cl. perfringens from various further processed products were usually less than 10/g, the three plating media showed similar specificity for this organism. All media supported good growth of reference strains of Clostridium perfringens but it was found that physiologically similar species, including Cl. absonum, Cl. paraperfringens and Cl. perenne also grew uninhibited in these media and produced colonies identical with those of Cl. perfringens, thus indicating the need for confirmatory tests for Cl. perfringens when examining natural samples.

The effects of various treatments on the microbial flora of whole poultry carcasses with particular reference to Staphylococcus aureus contamination

Experiments are described in which the effects of dipping defrosted eviscerated poultry carcasses, for various periods, in acetic, lactic, succinic and citric acids, hypochlorite solution containing 200 ppm free Cl2 and in water at temperatures from 70 degrees C to 100 degrees C on the microbial flora were determined. 2. Hot (70 degrees C) water dipping for 2 min appeared to be the treatment most likely to succeed in reducing Staph. aureus, giving reductions of staphylococci of from 63 to greater than 99%, without completely eliminating other organisms. 3. A storage experiment showed this method to be relatively safe, provided the carcasses were refrigerated to less than 3 degrees C as soon as possible after treatment and held at this temperature until adequately cooked.