Related Experiment Videos
The effect of membrane-bound beta-lactamase on linoleic acid sensitivity in Staphylococcus aureus
Abstract:
The presence of a plasmid conferring resistance to penicillin (PC plasmid, e.g. pI258blaI-) in Staphylococcus aureus NCTC 8325 increases the sensitivity of such a bacterium to the growth inhibitory effects of linoleic acid, whereas a plasmid conferring resistance to tetracycline does not affect linoleic acid sensitivity. The increased linoleic acid sensitivity of bacteria containing a PC plasmid may be related to the penicillinase protein itself since (i) strains having inducible penicillinase show increased sensitivity only after induction, (ii) strains in which penicillinase is directed from chromosomal or plasmid-borne genes show similar increased linoleic acid sensitivity and (iii) notwithstanding the above, the linoleic acid inhibitory effect is enhanced in a strain in which penicillinase activity is greatly reduced by a point mutation in the structural gene for penicillinase. The enhanced linoleic acid sensitivity seems to require the membrane-bound penicillinase since added extracellular penicillinase does not confer this sensitivity, and there appears to be a specific interaction between the membrane-bound penicillinase activity and linoleic acid.
Insights
Penicillin resistance plasmids in Staphylococcus aureus increase linoleic acid sensitivity. This effect is linked to membrane-bound penicillinase, not tetracycline resistance plasmids.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Staphylococcus aureus is a significant human pathogen.
- Antibiotic resistance plasmids are common in S. aureus.
- Linoleic acid exhibits antimicrobial properties.
Purpose of the Study:
- To investigate the effect of penicillin resistance plasmids on S. aureus sensitivity to linoleic acid.
- To elucidate the role of penicillinase in this observed sensitivity.
Main Methods:
- Comparative analysis of S. aureus strains with and without specific plasmids.
- Assessment of linoleic acid growth inhibition.
- Induction and mutation studies of penicillinase activity.
Main Results:
- Penicillin resistance plasmids (PC plasmids) significantly increased linoleic acid sensitivity in S. aureus.
- Tetracycline resistance plasmids did not affect linoleic acid sensitivity.
- Increased sensitivity correlated with penicillinase activity, particularly membrane-bound forms.
- Reduced penicillinase activity paradoxically enhanced linoleic acid inhibition.
Conclusions:
- Penicillin resistance plasmids confer increased linoleic acid sensitivity to S. aureus.
- Membrane-bound penicillinase activity plays a crucial role in this interaction.
- The precise mechanism involves a specific interaction between penicillinase and linoleic acid.