Mycological examination of herbal samples (collected from markets) showed the relationships of a large number of fungi including mycotoxin producers. Isolates of Aspergillus flavus, A. ochraceus and Fusariumoxysporum were screened respectively for aflatoxins (Afl), ochratoxin A and zearalenone production and a considerable number of these were found to be toxigenic. Ten different samples of each plant were also analyzed for mycotoxin contamination. Afl-B1 was the most frequently occurring mycotoxin, in fairly high concentrations (0.17-0.67μg/g) in all of the contaminated samples, whereas, ochratoxin A, citrinin and zearalenone were found in comparatively few samples.
Ammonium (NH4+) transport in the thermophilic, unicellular, non-nitrogen fixing cyanobacterium Synechococcus elongatus exhibited only one transport system (Km=37.03μM, Vmax=250nmol mg-1 protein min-1). A tenfold concentration gradient was established following 10min of incubation in 60μM NH4+. The rate of NH4+ transport was optimum at 50°C but no transport occurred at or below 30°C. Irreversible inactivation of the transport process occurred following exposure of the cells to 70°C. An Arrhenius plot of NH4+ uptake (35-50°C) showed that an activation energy of 20.9kcal/mol was required. The results suggested that the inability of the thermophilic cyanobacterium to grow at lower temperature could be due to unavailability of nutrients.
A total of 254 strains of the genera Nocardia, Rhodococcus, Amycolata, Amycolatopsis, Gordona and Pseudoamycolata were compared using numerical taxonomic techniques based on 273 physiological characters with the aid of miniaturized tests. Clustering was achieved using the unweighted pair group method with arithmetic averages (UPGMA) and the simple-matching coefficient (SSM) as the measure for similarity. Test error and overlap between the phena were within acceptable limits. Cluster groups were defined at the 87.4 to 91.3% levels (SSM). A total of 25 clusters were obtained in the SSM/UPGMA analysis beside 16 single member clusters, which in most cases were marker strains of different species. For the 25 clusters, containing two or more strains, a matrix comprising frequencies for positive results of 35 tests was constructed. The minimum number of diagnostic characters was selected by computer programs (CHARSEP, DIACHAR, MOSTTYP). The final matrix consisting of 35 tests versus 25 phena was theoretically evaluated using a computer program (MATIDEN) and out of 238 strains, a total of 157 strains (65.96%) were correctly identified with a Willcox probability>0.999, further 18 strains (7.56%) achieved Willcox probabilities above 0.900 and 2 strains (0.84%) were identified correctly with a Willcox probability above 0.800. Correct identification results were obtained for a total of 56 strains (23.52%), but with low Willcox probabilities ranging between 0.500 and 0.800. A total of 5 strains (2.10%) could not be assigned to the correct phenon. In a subsequent practical evaluation of the matrix 32 of 40 tested strains (80.0%) were correctly identified with Willcox probabilities above 0.900.
A peptidoglycan hydrolase (PGH), which causes the germination and lysis of the coat-stripped spores of Clostridium perfringens, was extracted from perfringens vegetative cells. The enzyme was partially purified and showed an MW of 125, 000 and a pI of 7.6. It was sensitive to a variety of monovalent and divalent cations and was inhibited by sulfhydryl-active agents. The sites of PGH action, the cell wall and the spore-cortex, were determined by the release of free amino groups from cell wall fragments and the release of soluble fluorescent products from fluorescamine-labelled cortical fragments of the C. perfringens spores. The enzyme appears distinct from the extracellular initiation protein produced by C. perfringens. PGH may be an autolysin with corticolytic activity.
The psychrotrophic Pseudomonad (4) of this study appears to be unique with regard to the production of a gel-like exopolymer (2, 3). If cells are repeatedly subcultured from the log phase, they produce minimal to no exopolymer upon inoculation of a permissive medium. However, if cells are allowed to reach maximum stationary phase during a particular growth cycle, and to persist for an appropriate period of time in this phase (the ‘aging’ period), the potential to make exopolymer accumulates and is expressed upon inoculation of a permissive medium. The nature of this potential is not known but a working hypothesis is that it is a regulatory compound that activates an enzyme (or enzymes) involved in exopolymer biosynthesis. This hypothesis stems from the following observations (2, 3): the accumulation of the potential during the aging period is time-, pH-, and temperature-dependent, and does not require new protein synthesis; there is a direct relationship between the amount of exopolymer produced and the number of aged cells in the inoculum; the potential accumulated in cells can be reduced by growth (cell divisions) in the nonpermissive medium prior to inoculation of a permissive medium; and exopolymer production occurs throughout the growth cycle of the bacterium and is not preceded by a lag period. In an attempt to understand the aging process at the molecular level, cell-free extracts from aged and unaged cells were prepared. This communication reports the stimulation of exopolymer production in unaged cells by adding portions of a cell-free extract to the permissive medium.