Pn. Rather et al., AN EXTRACELLULAR FACTOR REGULATING EXPRESSION OF THE CHROMOSOMAL AMINOGLYCOSIDE 2'-N-ACETYLTRANSFERASE OF PROVIDENCIA-STUARTII, Antimicrobial agents and chemotherapy, 41(8), 1997, pp. 1749-1754
The chromosomal anc(2')-Ia gene in Providencia stuartii encodes a hous
ekeeping 2'-N-acetyltransferase [AAC(2')-Ia] involved in the acetylati
on of peptidoglycan. In addition, the AAC(2')-Ia enzyme also acetylate
s and confers resistance to the clinically important aminoglycoside an
tibiotics gentamicin, tobramycin, and netilmicin. Expression of the na
c(2')-Ia gene was found to be strongly influenced by cell density with
a sharp decrease in aac(2')-Ia mRNA accumulation as cells approached
stationary phase, This decrease was mediated by the accumulation of an
extracellular factor, designated AR (for acetyltransferase repressing
)-factor. AR-factor was produced in both minimal and rich media and ac
ted in a manner that was strongly dose dependent, The activity of AR-f
actor was also pH dependent, with optimal activity at pH 8.0 and above
, Biochemical characterization of conditioned media from P. stuartii h
as shown that AR-factor is between 500 and 1,000 Da in molecular size
and is heat stable, In addition, AR-factor was inactivated by a variet
y of proteases, suggesting that it may be a small peptide.