The role of Beijerinckia spa and Klebsiella spp in stream litter decomposition was investigated using acetylene reduction method. Beijerinckia and Klebsiella were isolated during the winter and spring of 1980, from the leaves of sugar maple (Acer Saccharum), placed in Bell Creek, Muncie, Indiana. A nitrogen-free media was used to isolate Klebsiella. Both of these organisms were streaked separately on nitrogen-free agar slant tubes, flushed with argon and acetylene added. Gas chromatographic analysis were conducted on the innoculated tubes after incubation for 24 hours at 320 C. Beijerinckia spp, isolated from January, February, and April fixed between 4.48 x 10-7 moles and Klebsiella spp isolated during the same time period was between 1.47 to 8.10 x 10-8 moles. This study indicates that Beijerinckia is a better N2 fixer than Klebsiella in stream litter decomposition.

Like other aromatic hydrocarbons, benzene is a common soil and groundwater contaminant. It is recognized as a human carcinogen. Exposure of benzene can cause serious negative impacts on human health. Benzene is of major concern due to its toxicity and relatively high water solubility. Benzene is easily biodegraded by ubiquitous bacteria with the presence of free oxygen. However, soil and groundwater contamination with petroleum hydrocarbon often results in the development of anaerobic zones. Bioremediation has been considered as an advantageous alternative in terms of fairly low cost, process flexibility, and on-site utility for the treatment of contaminated soil and groundwater. However, benzene is particularly persistent under anaerobic condition even in the enhanced anaerobic biodegradation process. Although studies have shown that benzene biodegradation could occur under several reducing conditions, the in situ activities of anaerobic benzene degradation are generally low. Bioaugmentation rather than biostimulation may be applicable to accelerate biodegradation process. Successful bioaugmentation requires the inoculation of contaminated soil and groundwater with the strains or consortia of specific degrading capabilities. However, information of dominant species within the microorganisms for anaerobic benzene degradation is still limited. To address this problem, in this study, a benzene-degrading nitrate-reducing culture was established with soil contaminated by gasoline. A nitrate-reducing medium with sulphate, phosphate and other inorganic nutrient was employed to enhance anaerobic benzene degradation. BioSep BioTrap coupled with stable isotope probing and other molecular biological methods were used to identify key anaerobic benzene degraders. Members of genus Dokdonella spp., Pusillimonas spp., and Advenella spp. were found to be the dominant microorganisms during anaerobic benzene degradation, and were hypothesized to be benzene degrader under nitrate-reducing condition.

The aim of the work described here was to examine the antiprotozoal activity of the pericarp from Sapindus rarak DC (Sapindaceae) for its potential to defaunate the rumen, either partially or completely, without having a detrimental effect on the bacterial population and on rumen fermentation, and hence enhancing rumen productivity. An approach to improving microbial efficiency in the rumen is to eliminate protozoa (defaunation). Elimination of protozoa by chemical means is potentially the most convenient method. However, it is likely that some chemicals are not toxic specifically to the protozoa and probably kill other microorganisms and host cells in the rumen, therefore novel natural antiprotozoal agents are being sought. A possible role for saponins has been of interest to many researchers as saponins induce marked reductions in rumen protozoa numbers, particularly when the animal is fed on high-concentrate diets. The susceptibility of rumen protozoa and lack of susceptibility of rumen bacteria to saponins is explained by the reaction of saponins with membrane sterols, which are present only in eukaryotic membranes and not in prokaryotic bacterial cells. Recent in vitro results suggest that S. rarak exhibited higher immobilising activity and produce higher activity to lyse the cells compared to other saponin-containing plants. A preliminary study on the antiprotozoal activity of the active agent present in the pericarp of fruits of S. rarak, well known for the high saponin content of its fruits, was carried out. An antiprotozoal assay was developed. The results were consistent within experiments, but not between experiments, possibly due to the number of protozoa fluctuating widely with time. A study on the effect of Sapindus rarak on rumen bacteria, using a quantitative plating method, showed that there was no effect on rumen bacteria. Raw material and extract of pericarp of S. rarak were screened for their effects on rumen protozoa and bacteria (with a view to predicting its safety as a feed supplement and for its potential to defaunate the rumen, either partially or completely). The pericarp of S. rarak was extracted using selective extraction of saponins with CIS support. The fractions were collected and monitored by Thin Layer Chromatography (TLC). The active compounds were tested in vitro for toxicity to rumen protozoa by visual assessment of protozoal viability (Nottingham studies) and by measuring the degradation of labelled bacterial protein by rumen protozoa (Aberdeen studies). The influence of methanol extract of S. rarak on growth of pure cultures of rumen bacteria was also examined (Aberdeen studies). The results showed that the saponin fractions of S. rarak exhibit antiprotozoal activity as confirmed by visual assessment as well as by measurement of the breakdown of 14C-Ieucine-Iabelled Prevotella bryantti in rumen fluid incubated in vitro. No evidence was found of protozoal resistance to S. rarak. Inclusion of methanol extract of S. rarak in the growth medium of pure cultures of rumen bacteria had no effect, except that cellulolytic bacteria showed susceptibility. Extracts appeared in this study to prolong the lag phase following inoculation of Streptococcus bovis or inhibit the growth of Butyrifibrio fibrisolvens, Ruminococcos albus, and Ruminococcos flavefaciens. It seems that antibacterial properties were more pronounced against gram-positive bacteria, similar to the action ofionophores (McGuffey et al., 2001). A study on the effects of S. rarak on ruminal digestion, fermentation and ammonia concentration, using ruminally and duodenally cannulated dairy cows, showed that direct administration of S. rarak into the rumen did not decrease protozoal numbers in vivo. However, there were some indicators of selective activity against holotrichs. Changes in propionate concentration in the rumen and lack of change in microbial flow parameters suggest no adverse effects on other fermentation measures. Increased production of propionate is beneficial to the animal by affecting the capture of fermentation energy in the rumen. S. rarak caused a decrease in ammonia concentration. The observed ammonia levels represent a balance between the processes of degradation of feed protein and uptake of ammonia for synthesis of microbial protein. The lower ammonia levels could be due to higher incorporation of ammonia, peptide, or amino acids into microbial protein. In conclusion, S. rarak tested in this study has a great potential for suppressing rumen ciliate populations, but exerted negligible general effects on ruminal fermentation. Therefore, controlling rumen ciliate protozoa would be expected to lessen the dependence on protein supplementation under high-production conditions and would also be beneficial under conditions where the quantity of protein absorbed from the post-ruminal gut limits animal productivity, which occurs frequently in animals receiving low-quality tropical forages.

No description available.

Thesis (MApSc(MedicalLaboratorySce))--University of South Australia, 2003.

A unique opportunity to study both benthic microbial mats and modern stromatolites from a common niche is presented by the hypersaline environment of Hamelin Pool, Shark Bay, Australia. However, prior to this study, the microbial mat communities have not been well characterised. To investigate the taxonomic and functional diversity of Hamelin Pool pustular and smooth mats, and their similarity to Hamelin Pool stromatolites, culturing, culture-independent, and lipid analysis methods were employed. The cultured isolates obtained included heterotrophic bacteria similar to those obtained from other hypersaline environments, and 19 strains of cyanobacteria including potentially novel species. For the first time archaeal isolates were obtained from the pustular and smooth mats, and further characterisation of two strains indicated they might represent novel species of the genus Haloferax. Total DNA was extracted from the mats and 16S rRNA gene clone libraries were generated targeting the bacteria, cyanobacteria, archaea and eukarya. Both the pustular and smooth mat bacterial clone libraries were highly diverse, with 11 bacterial divisions represented, and Chao1 estimates of total species richness indicating ~3000 ??? 6000 species. Cyanobacterial and archaeal clone libraries revealed unique phylotypes associated with sediments of differing morphology. Statistically significant differences between the mat populations and Hamelin Pool stromatolite communities were identified using !-LIBSHUFF, a program designed to compare two 16S rRNA gene libraries. Signature lipid biomarkers were assessed for the pustular and smooth mats and an intertidal stromatolite from Hamelin Pool. Fatty acids (as methyl esters), wax esters, hydrocarbons, ether-bound lipids, hopanoids and sterols indicated the presence of oxygenic phototrophs, anoxygenic phototrophs, sulfate-reducing bacteria, sulfur-oxidising bacteria, heterotrophic bacteria and archaea in each of the sediment types. Limited contributions from diatoms, bivalves and their dinoflagellate symbionts, and from higher plant aerosols were also detected. Significantly, 2-methyl hopanoids and eight pseudohomologous series of branched alkanes with quaternary carbon centers were identified in the mats and stromatolites. Although differing in lithification status and precise microbial composition, the pustular and smooth mats are excellent analogues for the extant stromatolites of Hamelin Pool, and by corollary, provide a fascinating link to Precambrian microbial communities.

Thesis (M.D.S.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 181-209). Also available in electronic version.

Thesis (M. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaves 217-261) Also available in print.