Downloaded from www.microbiologyresearch.org by IP: 54.224.135.207 On: Sun, 03 Apr 2016 20:37:33 Journal of General Microbiology (I 973), 75,409-4 16 Printed in Great Britain 409 Morphological Mutants of Escherichia coli. Isolation and Ultrastructure of a Chain-forming envC Mutant By ANNIE RODOLAKIS, P. THOMAS .~ND J. STARKA Laboratoire de Chimie BactPrienne, C. N. R.S., Laboratoire de Cytologie Vkgktale and Laboratoire de Physiologie Microbieme, Centre Universitaire cle Marseille-Luniinj?, I 3009 Marseille, France (Received 15 November I 972) Non-conditional morphological mutant envC derived from Escherichia coli K- I 2 strain ~678, isolated after treatment with I-methyl-3-nitro- I -nitrosoguanidine, produced chains of bacteria on synthetic or rich media at 30 "C and 40 "C. It was sensitive to deoxycholate and less resistant to penicillin and rifampicin than the parent strain. In section under the electron microscope, the mutant showed greatly disorganized septum formation. Preliminary mapping of envC by conjugation located it near xyl. The morphological and physiological characteristics of eniC+ recombinants and the envC+ parent were identical. INTRODUCTION The mechanisms that control bacterial morphology and division are not clearly under- stood. Most mutations affecting these processes might be expected to be lethal. However, recent reports show that conditional and non-conditional morphological mutants can be obtained and used to learn something about their physiology and genetics. In their extensive study of thermosensitive mutants of Escherichia coli K-12, Kohiyama, Cousin, Ryter & Jacob (1966) observed many strains which grew normally at permissive temperatures but presented morphological, cytological and physiological alterations and irregularities in division at 40 "C. Three principal types of alterations were recognized : (i) fiIament and chain formation, (ii) irregular morphology ; and (iii) spherical forms. Several other authors isolated non-conditional or thermosensitive mutants of E. coli with characteristic morpho- logical alterations belonging to one of these groups (Normark, Boman & Matsson, 1962; Adler, Terry & Hardigree, 1968; Hirota, Ricard & Shapiro, I 971 ; Henning et al. 1972 ; Lazdunski & Shapiro, 1972). Another type of conditional mutant of E. coli is osmotically unstable at non-permissive temperature and the bacteria lyse (Kohiyama et al. 1966; Mangiarotti, Apirion & Schlessinger, I 966; Matsuzawa, Matsuhashi, Oka & Sugino, I 969). In most cases lysis can be prevented by osmotic stabilization. Morphological mutants and mutants defective in peptidoglycan synthesis were also re- ported for BacilIus subtilis, B. licheniJormis, Staphylococcus aureus and Agrobacteriuni tume- faciens (Rogers, McConnell & Burdett, 1968; Boylan & Mendelson, 1969; Chatterjee & Young, 1972; Fujiwara & Fukui, 1972; Good & Tipper, 1972). It appears that the morpho- logical defect is generally accompanied by a chemical and/or structural alteration of wall or cytoplasmic membrane and that the division is also affected in most cases. During our recent work with morphological mutants we have isolated a chain-forming mutant of Escherichia coli K-I2 which is not thermosensitive. In this first communication we 2 7-2