An rpoE‐like locus controls outer membrane protein synthesis and growth at cold temperatures and high pressures in the deep‐sea bacterium Photobacterium sp. strain SS9

Abstract

Many deep-sea bacteria have evolved specialized adaptations for life at cold temperatures and high pressures. A locus required for both psychro- and baro-adaptation in the psychrophilic, moderate barophile, Photobacterium species strain SS9 was identified among SS9 transposon mutants. DNA sequence analysis of this locus identified four complete open reading frames (ORFs), which appear to comprise an operon, and a fifth incomplete ORF. All transposon insertions isolated are in ORF3. Extensive sequence similarity exists between the translation products of ORFs 1-3 and a collection of gene products proposed to include alternative RNA polymerase sigma factors and modifiers of sigma-factor activity involved in extracytoplasmic sensing and regulation. Based on the similarity between ORF1 and Escherichia coli rpoE, we have tentatively designated this locus the rpoE locus. SS9 rpoE locus ORF3 insertion mutants showed altered abundances of numerous outer membrane proteins and were both baro- and psychro-sensitive. ORF3 mutant revertants that displayed enhanced high-pressure growth also displayed concomitant enhanced low-temperature growth. Most of these revertants possessed DNA rearrangements at the site of the transposon insertion, further demonstrating the importance of the rpoE locus to high-pressure and cold-temperature growth. Complementation analyses indicated that ORF3 functions in OMP synthesis regulation while ORF4 is required for baro- and psychro-adaptation.

Modulation of the Escherichia coliσE (RpoE) heat‐shock transcription‐factor activity by the RseA, RseB and RseC proteins

“…This organization may be important to maintain a tight balance of Rse protein levels. A similar organization is also observed for some of the other sigma factors belonging to the ECF family (Chi and Bartlett, 1995).…”

“…Over its entire length, the RseA protein shows a 40% amino acid identity with the ORF located downstream of the rpoE gene counterparts of Haemophilus influenzae and Photobacterium sp. SS9 (Chi and Bartlett, 1995). RseA also shares approx.…”

“…RseB shares the highest degree of sequence identity (51%) with ORF3 of Photobacterium sp. 559 (Chi and Bartlett, 1995), followed by ORF3 in H. influenzae (42%; Fleishmann et al, 1995) and MucB of P. aeruginosa (34%) (Schurr et al, 1996).…”

The σE‐mediated response to extracytoplasmic stress in Escherichia coli is transduced by RseA and RseB, two negative regulators of σE

“…Our current studies uncover only a minor role for RseC in (Chi and Bartlett, 1995). Primer-extension analysis of E. coli rseC revealed the existence of possible E -independent promoters upstream of rseC (A.…”

Honor thy symbionts

“…Previously characterized ECF-type factors control a variety of functions including expression of heat-shock genes in E. coli (67); biosynthesis of alginates (exopolysaccharides containing D-mannuronic and L-guluronic acids) in Pseudomonas aeruginosa (68); iron uptake in E. coli (69); nickel and cobalt efflux in Alcaligenes europhus (70); outer membrane protein synthesis in response to variations in osmolarity, barometric pressure, and temperature in Photobacterium spp. (71); and cellular responses to disulphide stress in Streptomyces coelicolor (72).…”