Formation of vesiculated large bodies of Staphylococcus aureus L-form in a liquid medium

A method is described in which cells of Staphylococcus aureus can be converted to vesiculated large bodies of L-form. When coccal cells were incubated in a liquid growth medium containing D-cycloserine, N-acetylmuramidase and subtilisin, a large number of vesiculated large bodies were formed. Electron microscopy revealed that development of internal vesicles arose after 6 hr of incubation.. When growth inhibitory concentrations of rifampicin, novobiocin, or chloramphenicol were added to the culture at 6 hr of incubation, small-sized nonvesiculated bodies were produced instead of vesiculated forms. The viability of cultures was reduced by rifampicin and novobiocin but not by chloramphenicol.     

The influence of green fluorescent protein incorporation on bacterial physiology: a note of caution

AIMS: To investigate the effect of green flourescent protein (GFP) incorporation on bacterial physiology. METHODS AND RESULTS: Comparisons were made between four different isogenic pairings of non-GFP-containing parents and their GFP-containing transformants with respect to growth rate and antimicrobial susceptibility. For the latter, sensitivities to 12 different antibiotics were measured initially by disc-diffusion assay, and then subsequently by generation of dose-dependent survival curves for 1 h exposure to different concentrations of tetracycline, ciprofloxacin and cetrimide USP. Whilst no significant difference in growth rate was observed, GFP-containing strains were uniformly and significantly more sensitive to all antimicrobial agents tested, excluding the beta-lactams, than their respective non-GFP-containing counterparts. CONCLUSIONS: GFP incorporation has a significant effect on bacterial physiology and can modulate antimicrobial susceptibility. SIGNIFICANCE AND IMPACT OF THE STUDY: Transformation with GFP can affect the physiology of bacterial cells. This may therefore affect the quality and accuracy of data generated depending on the application for which GFP is used.     

Influence of cultivation conditions on the production of staphylocoagulase by Staphylococcus aureus 104.

High yields of staphylocoagulase from Staphylococcus aureus 104 were obtained in a simple salts medium supplement with glycerol, casein hydrolysate and three vitamins. Conditions of oxygen-limitation (dissolved oxygen concentration less than 2%), a pH of 7.4, a temperature of 35 degrees C and a 1 in 10 inoculum of overnight culture were required for optimal yields of staphylocoagulase.     

Localized perforation of the cell wall by a major autolysin: atl gene products and the onset of penicillin-induced lysis of Staphylococcus aureus.

We investigated the cell surface localization of the atl gene products of Staphylococcus aureus exposed to a lytic concentration (4 MIC) of penicillin G (PCG) by means of immunoelectron microscopy using anti-62-kDa N-acetylmuramyl-L-alanine amidase or anti-51-kDa endo-beta-N-acetylglucosaminidase immunoglobulin G. Protein A-gold conjugates reacting with antigen-antibody complex localized at sites of defects of the cell wall at the nascent cross wall. Anti-62-kDa N-acetylmuramyl-L-alanine amidase or anti-51-kDa endo-beta-N-acetylglucosaminidase immunoglobulin G inhibited the decreased turbidity caused by PCG-induced lysis and the formation of defects in the wall. The autolysis-defective mutant, S. aureus RUSAL2 (atl::Tn551), exposed to 4 MIC of PCG resisted autolysis and formation of the wall defect. These results suggest that activation or deregulation of the atl gene products at localized sites where formation of new cross wall was disturbed by PCG causes small defects in the cell wall in situ, eventually leading to general autolysis.     

A note on the isolation of Staphylococcus aureus from raw minced meat

Conventional Baird-Parker medium (BP) and three modified BP-type media were tested for their suitability to detect and to enumerate Staphylococcus aureus in raw minced meat. BP with pig plasma gave the most rapid results without the need for extensive confirmatory tests. A method which combined a liquid modification of BP medium with BP agar supplemented with acriflavine, polymyxin and sulphamezathine, was cheaper, more sensitive, and did not necessitate additional identification. Conventional BP incubated at 37 and 43C yielded less satisfactory results.     

A note on the isolation of Staphylococcus aureus from raw minced meat

Conventional Baird-Parker medium (BP) and three modified BP-type media were tested for their suitability to detect and to enumerate Staphylococcus aureus in raw minced meat. BP with pig plasma gave the most rapid results without the need for extensive confirmatory tests. A method which combined a liquid modification of BP medium with BP agar supplemented with acriflavine, polymyxin and sulphamezathine, was cheaper, more sensitive, and did not necessitate additional identification. Conventional BP incubated at 37 degrees and 43 degrees C yielded less satisfactory results.