scholarly journals Appearance of Low Molecular Weight DNA in a Rec- Mutant of Escherichia coli K12 Irradiated with X-rays

1968 ◽  
Vol 9 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Mitsuoki MORIMYO ◽  
Zen-ichiro HORII ◽  
Kenshi SUZUKI
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Low Molecular Weight ◽  
X Rays ◽  
Escherichia Coli K12

Interference with Murein Turnover Has No Effect on Growth but Reduces β-Lactamase Induction in Escherichia coli

1999 ◽  
Vol 181 (23) ◽  
pp. 7192-7198 ◽  
Author(s):  
Angelika R. Kraft ◽  
Julia Prabhu ◽  
Astrid Ursinus ◽  
Joachim-Volker Höltje
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Enterobacter Cloacae ◽  
Low Molecular Weight ◽  
Specific Inhibition ◽  
Triple Mutant ◽  
Induced Expression ◽  
Lytic Transglycosylases ◽  
Reduced Rate ◽  
Specific Inhibitors

ABSTRACT Physiological studies of a mutant of Escherichia colilacking the three lytic transglycosylases Slt70, MltA, and MltB revealed that interference with murein turnover can prevent AmpC β-lactamase induction. The triple mutant, although growing normally, shows a dramatically reduced rate of murein turnover. Despite the reduction in the formation of low-molecular-weight murein turnover products, neither the rate of murein synthesis nor the amount of murein per cell was increased. This might be explained by assuming that during growth in the absence of the major lytic transglycosylases native murein strands are excised by the action of endopeptidases and directly reused without further breakdown to muropeptides. The reduced rate of murein turnover could be correlated with lowered cefoxitin-induced expression of β-lactamase, present on a plasmid carrying theampC and ampR genes from Enterobacter cloacae. Overproduction of MltB stimulated β-lactamase induction, whereas specific inhibition of Slt70 by bulgecin repressedampC expression. Thus, specific inhibitors of lytic transglycosylases can increase the potency of penicillins and cephalosporins against bacteria inducing AmpC-like β-lactamases.

Monoclonal antibodies against the capsular K antigen of Escherichia coli (09: K30(A): H12): characterisation and use in analysis of K antigen organisation on the cell surface

1988 ◽  
Vol 34 (10) ◽  
pp. 1159-1165 ◽  
Author(s):  
Mary K. Homonylo ◽  
Sheila J. Wilmot ◽  
Joseph S. Lam ◽  
Leslie A. MacDonald ◽  
Christopher Whitfield
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Monoclonal Antibodies ◽  
Cell Surface ◽  
Molecular Probes ◽  
Low Molecular Weight ◽  
Gel Chromatography ◽  
E Coli ◽  
Capsular Antigen ◽  
K Antigen

Monoclonal antibodies were produced against the capsular antigen of Escherichia coli serotype K(A)30, using a mouse hybridoma system. The antibodies also recognised the chemically identical capsular polysaccharide produced by Klebsiella K20. Chemical modification of the K30 polysaccharide indicated that the glucuronic acid residues found in the E. coli K30 capsular antigen were important in the epitope recognised by these antibodies. Use of the antibodies as molecular probes revealed the presence of two discrete forms of the K30 antigen. One form was comprised of high molecular weight polysaccharide, present as a surface capsular layer. The second form of the antigen was of low molecular weight and was associated with lipopolysaccharide fractions from cell surface polysaccharide extracts. Separation of lipopolysaccharide fractions using gel chromatography in the presence of detergent showed that the low molecular weight K-antigenic fraction comigrated with a lipopolysaccharide lipid A core fraction present in encapsulated E. coli K30 bacteria but absent in acapsular mutants.

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