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Pseudomonas saccharophila could fix N$ sb2$ under micro-aerobic conditions, heterotrophically and chemolithotrophically. Uptake hydrogenase activity under heterotrophic conditions had no effect on the O$ sb2$ sensitivity of nitrogenase. H$ sb2$ induced whereas sucrose and O$ sb2$ repressed hydrogenase synthesis. Sucrose and O$ sb2$ did not inhibit hydrogenase activity. Hydrogenase and urease were located in the membrane and soluble fractions, respectively. Nickel stimulated growth, hydrogenase expression, and nitrogenase activity under N-limited chemolithotrophic conditions. Hydrogenase synthesis specifically required nickel and its repression by O$ sb2$ was alleviated by increasing the nickel concentration. Incorporated $ sp{63}$Ni$ sp{2+}$ was about 3 times higher in the soluble than in the membrane fraction. The short-term uptake of nickel was energy-independent and had an apparent $K sb{m}$ of 31.7 uM and $V sb{max}$ of 3.8 nmol Ni$ sp{2+}$ (mg protein)$ sp{-1}$min$ sp{-1}$. / A counting method for heterotrophic and chemolithotrophic N$ sb2$-fixing H$ sb2$-oxidizing bacteria was developed. The white bean rhizosphere soil showed relatively high numbers of these bacteria.

Four meat spoilage organisms were grown at 4$ sp circ$C for 7 d, in an aqueous extract of meat (Meat Juice Medium), and the levels of various nutrients in the extracts were measured. At an agitation rate of 50 rev$ cdot$min$ sp{-1},$ the four species reached viable counts of 10$ sp8$ Colony Forming Units (CFU)$ cdot$ml$ sp{-1},$ and the order of nutrient utilization was as follows: (1) glucose, (2) gluconate and urea, (3) glycerol, (4) glucose-6-phosphate. Several substrates were still present in the growth medium at the end of the growth period, namely lactate, glucose-6-phosphate and the two unknowns. At a higher agitation rate (100 rev$ cdot$min$ sp{-1}),$ the non-fluorescent pseudomonad reached final counts of ca. 10$ sp{10}$ CFU$ cdot$ml$ sp{-1},$ 2 logs higher than those of the other three organisms present in the mixed culture. The order of nutrient utilization was: (1) glucose, (2) gluconate, urea and glycerol, (3) lactate and glucose-6-phosphate, (4) unknowns 1 and 2. At day 7, none of the nine substrates studied remained in the growth medium.

Reprints to two articles published by the author held in pocket in back of publication / x, 158, xxvi leaves : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology, 1974

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