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[Optical density changes in bacterial protoplast suspensions exposed to membrane-active antibiotics]
Antibiotiki
|October 1, 1984
Summary
Membrane active antibiotics can cause bacterial protoplast swelling, increasing suspension optical density (OD) without lysis. This swelling indicates reduced osmotic stability, a key effect of these antimicrobial agents.
Area of Science:
- Microbiology
- Biophysics
Background:
- Membrane-active antibiotics like gramicidin S disrupt bacterial cell membranes.
- Antibiotic effects on bacterial protoplasts are crucial for understanding antimicrobial mechanisms.
Purpose of the Study:
- To investigate the sub-lytic effects of membrane-active antibiotics on bacterial protoplasts.
- To characterize the changes in optical density (OD) and protoplast size in response to sub-lytic antibiotic concentrations.
Main Methods:
- Treatment of Micrococcus lysodeikticus protoplasts with varying concentrations of membrane-active antibiotics.
- Measurement of suspension optical density (OD).
- Determination of protoplast diameter using the Klenin et al. method.
Main Results:
- Sub-lytic concentrations of antibiotics caused a 10-30% increase in suspension OD, indicating protoplast swelling.
- The observed OD increase correlated with a 15% increase in protoplast diameter.
- No protoplast agglutination was observed under conditions of OD increase.
Conclusions:
- Membrane-active antibiotics, at sub-lytic doses, decrease protoplast osmotic stability, leading to swelling.
- Protoplast swelling, evidenced by increased OD, is a measurable response to sublethal antibiotic action.
- This swelling effect precedes lysis and offers insights into early-stage antibiotic-membrane interactions.