Extragenic Suppressors of Growth Defects in msbB Salmonella
AUTOR(ES)
Murray, Sean R.
FONTE
American Society for Microbiology
RESUMO
Lipid A, a potent endotoxin which can cause septic shock, anchors lipopolysaccharide (LPS) into the outer leaflet of the outer membrane of gram-negative bacteria. MsbB acylates (KDO)2-(lauroyl)-lipid IV-A with myristate during lipid A biosynthesis. Reports of knockouts of the msbB gene describe effects on virulence but describe no evidence of growth defects in Escherichia coli K-12 or Salmonella. Our data confirm the general lack of growth defects in msbB E. coli K-12. In contrast, msbB Salmonella enterica serovar Typhimurium exhibits marked sensitivity to galactose-MacConkey and 6 mM EGTA media. At 37°C in Luria-Bertani (LB) broth, msbB Salmonella cells elongate, form bulges, and grow slowly. msbB Salmonella grow well on LB-no salt (LB-0) agar; however, under specific shaking conditions in LB-0 broth, many msbB Salmonella cells lyse during exponential growth and a fraction of the cells form filaments. msbB Salmonella grow with a near-wild-type growth rate in MSB (LB-0 containing Mg2+ and Ca2+) broth (23 to 42°C). Extragenic compensatory mutations, which partially suppress the growth defects, spontaneously occur at high frequency, and mutants can be isolated on media selective for faster growing derivatives. One of the suppressor mutations maps at 19.8 centisomes and is a recessive IS10 insertional mutation in somA, a gene of unknown function which corresponds to ybjX in E. coli. In addition, random Tn10 mutagenesis carried out in an unsuppressed msbB strain produced a set of Tn10 inserts, not in msbB or somA, that correlate with different suppressor phenotypes. Thus, insertional mutations, in somA and other genes, can suppress the msbB phenotype.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=95446Documentos Relacionados
- Escherichia coli msbB Gene as a Virulence Factor and a Therapeutic Target
- Isolation and characterization of the Escherichia coli msbB gene, a multicopy suppressor of null mutations in the high-temperature requirement gene htrB.
- The msbB Mutant of Neisseria meningitidis Strain NMB Has a Defect in Lipooligosaccharide Assembly and Transport to the Outer Membrane
- An msbB Homologue Carried in Plasmid pO157 Encodes an Acyltransferase Involved in Lipid A Biosynthesis in Escherichia coli O157:H7
- Extragenic Suppressors of Mar2(sir3) Mutations in Saccharomyces Cerevisiae