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Proteolytic activity in a batch culture of Bacteroides ruminicola R8/4 was maximal and largely (greater than 90%) cell-associated during the mid-exponential phase of growth. The cell-bound protease was not inactivated during storage at --70% C, was not significantly affected by pH over the range 5.9 to 8.2, but was subject to substrate inhibition by Fraction 1 protein (ribulose-1,5-bisphosphate carboxylase; EC 4.1.1.39) and was most active in the presence of thiol reagents. Radioactive Fraction 1 protein was hydrolysed by non-growing and growing cells of B. ruminicola R8/4 with the production of peptides and free amino acids. Deaminase activity was absent. Radioactive amino acids were incorporated into bacterial proteins from [14C]Fraction 1 protein without substantial change in specific radioactivity.

The complete nucleotide sequence of the xynA gene coding for a xylanase (XYLA) expressed by Pseudomonas fluorescens subspecies cellulosa, has been determined. The structural gene consists of an open reading frame of 1833 bp followed by a TAA stop codon. Confirmation of the nucleotide sequence was obtained by comparing the predicted amino acid sequence with that derived by N-terminal analysis of purified forms of the xylanase. The signal peptide present at the N terminus of mature XYLA closely resembles signal peptides of other secreted proteins. Truncated forms of the xylanase gene, in which the sequence encoding the N-terminal signal peptide had been deleted, still expressed coli. XYLA contains domains which are homologous to an endoglucanase expressed by the same organism. These structures include serine-rich sequences. Bal31 deletions of xynA revealed the extent to which these conserved sequences, in XYLA, were essential for xylanase activity. Downstream of the TAA stop codon is a G + C-rich region of dyad symmetry (delta G = 24 kcal) characteristic of E. coli Rho-independent transcription terminators.

1. Some members of the genus Butyrivibrio, including a general fatty acid auxotroph (strain S2), contain as a major part of their complex lipids a high-molecular-weight component that is probably formed by the union of two fatty acid chains [Hazlewood & Dawson (1979) J. Gen. Microbiol. 112, 15--27]. 2. Proton and 13C n.m.r. and i.r. and mass spectroscopy were used to examine a homologous series of these moieties and, in addition, the hydrocarbon derivative of one homologue and several synthetic compounds. 3. The results indicate that the high-molecular-weight components are a series of long-chain dicarboxylic acids containing vicinal dimethyl branching, located near the centre of the chain.