To carry out a genetic analysis of the degradation and utilization of chitin by Serratia marcescens 2170, various Tn5 insertion mutants with characteristic defects in chitinase production were isolated and partially characterized. Prior to the isolation of the mutants, proteins secreted into culture medium in the presence of chitin were analyzed. Four chitinases, A, B, C1, and C2, among other proteins, were detected in the culture supernatant of S. marcescens 2170. All four chitinases and a 21-kDa protein (CBP21) lacking chitinase activity showed chitin binding activity. Cloning and sequencing analysis of the genes encoding chitinases A and B of strain 2170 revealed extensive similarities to those of other strains of S. marcescens described previously. Tn5 insertion mutagenesis of strain 2170 was carried out, and mutants which formed altered clearing zones of colloidal chitin were selected. The obtained mutants were divided into five classes as follows: mutants with (i) no clearing zones, (ii) fuzzy clearing zones, (iii) large clearing zones, (iv) delayed clearing zones, and (v) small clearing zones. Preliminary characterization suggested that some of these mutants have defects in chitinase excretion, a negatively regulating mechanism of chitinase gene expression, an essential factor for chitinase gene expression, and a structural gene for a particular chitinase. These mutants could allow researchers to identify the genes involved in the degradation and utilization of chitin by S. marcescens 2170.The number of studies dealing with bacterial chitinasestheir biochemical properties, the structure of the genes encoding them, the catalytic mechanism involved, and their tertiary structures-has been increasing rapidly. The hydrolysis of chitin by chitinases is the most critical step in the degradation and utilization of chitin by bacteria. However, the study of chitinases is not sufficient to elucidate the process by which chitin is degraded and utilized by bacteria. The process involves a number of steps, including the recognition of chitin outside of the cell, the induction of chitinases, the maintenance of proper levels of chitinase production, and the incorporation and catabolism of degradation products. In this study our intent was to identify the genes involved in the degradation and utilization of chitin. Our long-term goal is to answer the following questions. How do bacteria recognize chitin? How is chitinase production induced and regulated? Why do chitinolytic bacteria produce multiple chitinases? How are degradation products processed? Our ultimate goal in these studies is a general understanding of how bacterial cells degrade and utilize chitin.We have studied the chitinase system of Bacillus circulans WL-12 and have provided comprehensive findings on biochemical properties, structure-function relationships, the identification of essential amino acid residues for catalytic activity, and the mechanisms by which multiple chitinases are generated (1, 2, 4, 23, 31-35). However, this bacterium is not a suitable...

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Nodulated soybean (Glycine max [L.] Merr.) plants wereprotein showed a main band at 100 kDa on sodium dodecyl sulfate (SDS)-PAGE. The K m value for nitrate was 0.16 mM, grown in a nitrogen-free liquid culture medium prepared with and the highest activity was obtained at around pH 7.5. These distilled water. The cytosol fraction from root nodules showed characteristics are very similar to the inducible type of nitrate a significant level of NADH-dependent nitrate reductase activity, even when the root did not show activity. This nitrate reductase, previously purified from soybean leaves. The develreductase was purified by column chromatography and native opmental change in activity of this enzyme corresponded to polyacrylamide gel electrophoresis (PAGE). The purified that in nitrogenase activity.

A multinucleated giant cell tumor developed in the left renal pelvis of a 60-year-old man. The tumor was morphologically indistinguishable from giant cell tumor of bone and considered to be both primary and benign, with a follow-up period of one year and no evidence of either recurrence or metastasis.