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Differences in the 16S rRNA genes (16S rDNA) which can be used to discriminate Listeria monocytogenes from Listeria innocua have been detected. The 16S rDNA were amplified by polymerase chain reaction with a set of oligonucleotide primers which flank a 1.5-kb fragment. Sequence differences were observed in the V2 region of the 16S rDNA both between L. monocytogenes Scott A and L. innocua and between different L. monocytogenes serotypes. Although L. monocytogenes SLCC2371 had the same V2 region sequence as L. innocua, the two species were different within the V9 region at nucleotides 1259 and 1292, in agreement with previous studies (R.-F. Wang, W.-W. Cao, and M. G. Johnson, Appi. Environ. Microbiol. 57:3666-3670, 1991). Intraspecies discrimination ofL. nwnocytogenes strains was achieved by using the patterns generated by random amplified polymorphic DNA primers. Although some distinction can be made within the L. monocytogenes species by their 16S rDNA sequence, a far greater discrimination within species could be made by generating random amplified polymorphic DNA patterns from chromosomal DNA. By using a number of 10-bp primers, unique patterns for each isolate which in all cases examined differentiate between various L. monocytogenes serotypes, even though they may have the same 16S rRNA sequences, could be generated.

The degradation rate of atrazine in floodplain soils under natural grasslands and cropped fields in the Liverpool Plains, NSW, was studied under laboratory incubation and in glasshouse bioassays, and related to soil properties including microbial community analysis by t-RFLP. The experiments were part of a broader study aiming to manage pesticides in the environment using vegetative filters (biofilters). The soils differed in their atrazine treatment history. Degradation rate (half-life) in cropped soil was more rapid (≈2 to 7 days) than in 2 grassland soils (≈8 to ≈22 days). Bioassays in the glasshouse using oats and soybeans supported this finding. The t-RFLP analysis disclosed the presence of 2 consortia of bacterial species that are reported in the literature to degrade atrazine. These were: (i) Rhodococcus sp, Pseudomonas aeruginosa, and Clavibacter michiganense and (ii) Acinetobacter sp., Pseudomonas sp., and Streptomyces sp. Their dynamics during incubation suggested that they might have been responsible for the more rapid atrazine degradation in the cropped soil. The enhanced atrazine degradation in cropped soil was also associated with lower concentrations of soil organic C and percentage of light fraction carbon compared with grassland soils, suggesting that atrazine provided an additional source of N and C to organisms that can quickly degrade the herbicide. The finding of relatively short atrazine half-life has implications for the effectiveness of the herbicide, as well as for the loads of pesticide potentially entering the environment. The results suggest there is little risk of atrazine accumulating in biofilters and causing damage.

Five different species of selected broad-spectrum antibiotic lactic acid bacteria isolated from extremely high-cold areas were used as starters to ferment indigenous forage oats and wheatgrass under rigid alpine climatic conditions. The five isolates were Lactobacillus plan-tarum QZ227, Enterococcus mundtii QZ251, Pediococcus cellicola QZ311, Leuconostoc mesenteroides QZ1137 and Lactococcus lactis QZ613, and commercial Lactobacillus plan-tarum FG1 was used as the positive control and sterile water as the negative control. The minimum and maximum temperatures were −22˚C and 23˚C during the fermentation process , respectively. The pH of wheatgrass silage fermented by the QZ227 and FG1 inocula reached the expected values (4.15) although the pathogens detected in the silage should be further investigated. All of the inocula additives used in this study were effective in improving the fermentation quality of oat silage as indicated by the higher content of lactic acid, lower pH values (4.17) and significant inhibition of pathogens. QZ227 exhibited a fermentation ability that was comparable with the commercial inoculum FG1 for the whole process, and the deterioration rate was significantly lower than for FG1 after storage for 7 months. The pathogens Escherichia coli, mold and yeast were counted and isolated from the deteriorated silage. E. coli were the main NH 3-N producer while F. fungi and yeast produced very little.

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