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A fungal isolate, Arthrographis sp. strain F4, when grown in shake-flask culture, produced cellulolytic and xylanolytic enzymes optimally at 30°C with an initial pH of 5.0 to 6.0. Coarsely-ground filter paper was the most suitable carbon substrate for production of the enzymes. Inorganic nitrogen sources gave higher activities of the enzymes than organic nitrogen sources: NH4NO3 and yeast extract was the most effective combination. Significant stimulation (P<0.05) of enzyme production was achieved with 0.1% (v/v) Tween 80.

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A thermostable amylase, possibly a beta-amylase from Thermoactinomyces sp. no. 2 isolated from soil, is reported. The enzyme was purified 36-fold by acetone precipitation, ion-exchange chromatography, and Sephadex G-200 gel filtration, and the molecular weight was estimated at 31,600. The enzyme was characterized by demonstration of optimum activity at 60 degrees C and pH 7 and by retention of 70% activity at 70 degrees C (30 min). It was stimulated by Mn and Fe but strongly inhibited by Hg. Maltose was the only detectable product of hydrolysis of starches and was quantitatively highest in plantain starch hydrolysate.

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The aerobic bacteria associated with soft rot in onions (Allium cepa) were isolated and identified as a Vibrio sp., Micrococcus epidermidis, Pseudomonas cepacia, an Acinetobacter sp., a Xanthomonas sp., Bacillus polymyxa, and Bacillus megaterium. With the cup-plate assay method, no pectin hydrolase could be detected from any of these isolates when they were cultured in pectin medium, but lyase and pectinesterases were detectable. Onion tissue cultures showed pectin hydrolase activity for P. cepacia and B. polymyxa and lyase and pectinesterase activities for all of the isolates, usually at higher levels of activity than those of the pectin medium culture filtrates. In both culture media, Vibrio sp. showed the highest lyase and pectinesterase activities. In the viscometric test, all of the isolates achieved at least a 50% decrease in viscosity for lyase enzyme, with M. epidermidis and Vibrio sp. recording viscosity decreases as high as 83%. The ability to cause soft rot in onion bulbs was demonstrated by P. cepacia and Xanthomonas sp. Benzoic acid at a concentration of 0.8 mg/ml caused total suppression of enzyme production, whereas sodium benzoate at this concentration reduced pectinesterase production by 71% and lyase production by 72%. The possible use of these preservatives in the control of soft rot in onions is noted.

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Anaerobic and facultatively anaerobic bacteria associated with soft rot of yam (Diascorea rotundata) were isolated by the looping-out method and found to consist of Clostridium (three isolates), Corynebacterium (three isolates), Vibrio (one isolate), and Bacillus lentus (one isolate). Enzyme assay for hydrolase, lyase, and pectinesterase activities by the cup-plate method showed that except for Vibrio sp., B. lentus, and two isolates of Corynebacterium no pectinase activity could be detected for organisms cultured on pectin medium. Most of the cultures on yam tissue, however, showed activities for the three enzymes. The viscometric assay for hydrolase and lyase enzymes indicated a significant level of hydrolase activity (a 40.90% decrease in viscosity for Vibrio sp. and Corynebacterium spp.), but no lyase activity for most of the isolates. Two isolates of Corynebacterium and B. lentus caused changes in fresh yams suggestive of soft rot.

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A total of 550 E. coli isolates--250 from apparently healthy, and 300 from diarrhoeic West African pigmy goats were tested for colicinogenicity. 33.2% of strains from apparently healthy animals were colicinogenic as against 56% recorded for strains from animals with diarrhoea. Of the 251 colicinogenic E. coli strains from both groups of animals, 76.5% were Type I while 23.5% belonged to Type II. Identified colicins from the healthy animals consisted of types G, K, E2, A and V in decreasing frequency of occurrence, whereas those from goats with diarrhoea were made up of types V, B, E1, G, E2, E3, and Ia also in decreasing frequency of occurrence. In contrast to isolates from healthy animals, there was a marked variation in the colicin spectra of Types I and II E. coli from the diarrhoeic animals--that of Type I being much broader. The Public Health significance of possible transfer of multiple drug resistance from colicinogenic E. coli strains to other enterobacteria is also discussed.

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A total of 96 Bacillus species consisting of B. licheniformis, B. pumilus, B. subtilis, B. megaterium and B. polymyxa isolated from smoked meat were screened for both lecithinase and toxin production. Lecithinase production was found to be wide-spread among these species and to be strain specific. A high percentage of the tested species (66.7-100%) was strongly lecithinase positive. Like lecithinase, toxin production is wide-spread among the Bacillus species and is equally strain specific. With the exception of the B. pumilus isolates, an absolute correlation between lecithinase and toxin production could not be established among the tested isolates. In B. pumilus both lecithinase and toxin are detectable in the culture filtrate after three hours incubation but while maximal lecithinase synthesis occurs within three hours, maximal toxin production is not attained within 15 h incubation. B. pumilus toxin proved toxic for mice but not for rats.

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The Salmonella, Arizona, Shigella and Aeromonas contents of 39 snails (Achatina achatina) were investigated. Serotyping of the Salmonella isolates revealed the presence of S. manhattan, S. ndolo, S. reading, S. uppsala, and S. typhimurium. Six of 18 Shigella isolates were identified as Sh. sonnei while all the Aeromonas proved to be A. hydrophila. Fifty eight percent of these A. hydrophila isolates were enterotoxigenic, and their toxin was shown to be heat labile. All the A. hydrophila strains were both protease positive and haemolytic: 66.7% being both alpha and beta haemolytic while 33.3% showed only alpha haemolysis.

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