Morphological changes associated with novobiocin resistance in Bacillus licheniformis

Area of Science:

• Microbiology
• Bacterial Genetics
• Cell Biology

Background:

• Novobiocin is an antibiotic that affects bacterial growth.
• Novobiocin resistance can arise spontaneously in bacterial populations.
• Gram-positive and gram-negative bacteria may respond differently to novobiocin.

Purpose of the Study:

• To isolate and characterize spontaneous novobiocin-resistant mutants of Bacillus licheniformis.
• To investigate the phenotypic changes associated with novobiocin resistance in B. licheniformis.
• To compare the effects of novobiocin on gram-positive and gram-negative organisms.

Main Methods:

• Isolation of spontaneous novobiocin-resistant mutants from Bacillus licheniformis ATCC 9945.
• Microscopic observation of mutant morphologies in the presence and absence of novobiocin.
• Comparison of observed phenotypes with existing literature on novobiocin effects.

Main Results:

• Novobiocin-resistant mutants were obtained at a frequency of 3 in 10^6 organisms.
• Most mutants exhibited pleiotropic alterations in colonial and cell morphology.
• A specific mutant (nov-12) displayed abnormal cell chaining and filamentation, with altered septation under novobiocin pressure.
• Genetically abolishing low-level novobiocin sensitivity in B. licheniformis rendered it susceptible to novobiocin actions similar to gram-negative organisms.

Conclusions:

• Novobiocin resistance in B. licheniformis is associated with significant morphological changes.
• The primary action of novobiocin may differ between gram-positive and gram-negative bacteria.
• Novobiocin resistance can be a valuable tool for isolating gram-positive mutants with altered cell walls.