Erwinia chrysanthemi produced several pectate lyases (EC 4.2.2.2) and endocellulases (EC 3.2.1.4) which were largely secreted into the culture medium. Mutants deficient in the secretion mechanism for these enzymes were obtained by chemical and insertion mutagenesis. Further study of one such mutant revealed that both enzyme activities were retained simultaneously within the periplasmic space.

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Erwinia chrysanthemi 3937 secretes four major pectate lyase isoenzymes (PL, EC 4.2.2.2) and one endocellulase (Cx, EC 3.2.1.4). A genomic library of this strain was constructed in the Lambda L47‐1 vector, and screened for the presence of PL and Cx on pectate and caboxymethylcellulose agar. Among the seven Cx‐positive phage clones, three were shown to encode an enzyme of the same mol. wt. as the one found in the culture supernatant of strain 3937. The 34 PL‐positive phage clones were analyzed by electrofocusing and could, according to the PL they produced, be arranged in five classes. Phages from three classes produced three different single PL, named PLb, c and d. No common fragment was evidenced between the inserts of the phages of these three classes. This demonstrated that, in strain 3937, PLb, C, and d were encoded by three different genes called pelB, C, and D. Furthermore, our results suggest the existence of two additional genes encoding PLa and e. In addition, a pectin methylesterase gene was found closely linked to pelD.

899Extracellular proteolytic enzyme activity has been detected in cultures of Erwinia chrysanthemi. This activity, which appears when the cells are grown in the presence of peptides, is rather unstable. A hyperproteolytic mutant was isolated which produces two proteases of apparent polypeptide molecular mass of 50 and 55 kDa, respectively. The 50 kDa protease, which is produced in the largest amounts, has been purified to near homogeneity. It has the properties of a neutral serine protease. The 50 and 55 kDa proteases are unrelated antigenically. Preliminary evidence suggests that both proteases are also produced by the wild-type strain, but that they are either produced in much smaller quantities or are much less stable.