Studies on the bacterial spore coat. (8) On the SDS-DTT extract from Bacillus megaterium spores

Interaction of iodine with Bacillus subtilis spores and spore forms

Buffered solutions of iodine (pH 7.0) were effective against Bacillus subtilis spores, but concentrations and contact times for effective sporicidal action were relatively high. Concentrations of 500 to 1000 ppm available iodine with a contact time of 30-45 min were required to produce a 3-5 log reduction. Treatment of spores with agents which caused progressive extraction of coat protein and cortex hexosamine was associated with increased sensitivity to iodine. Treatment of spores with iodine produced extraction of spore coat protein which was potentiated in the presence of NaOH, but there was no evidence of breakdown of cortex hexosamines or release of dipicolinic acid, either from intact spores or spore protoplasts. Sporicidal concentrations of iodine stimulated the uptake of (32P) phosphate over an initial period of 30-40 min, but phosphate then leaked from the cells; 1000 ppm available iodine produced total loss within 60 min. Results of this investigation are consistent with previous findings which suggest that the resistance of spores to biocides is related to the barrier properties of the spore outer layers and that the sporicidal action of halogen-releasing agents is related to their ability to cause coat and cortex degradation, leading to rehydration of the spore protoplast and allowing diffusion to their site of action on the underlying protoplast.

Interaction of Bacillus subtilis spores with sodium hypochlorite, sodium dichloroisocyanurate and chloramine-T

Solutions of chlorine-releasing agents (CRAs) show varying activity against Bacillus subtilis spores; sodium hypochlorite (NaOCl) shows higher activity than sodium dichloroisocyanurate (NaDCC) which is more active than chloramine-T. Investigations with coat- and cortex-extracted spores indicate that resistance to CRAs depends not only on the spore coat but also the cortex. Whereas extraction of alkali-soluble coat protein increased sensitivity to NaOCl and NaDCC, degradation of coat and cortex material was required to achieve significant activity with chloramine-T. NaOCl (in the presence and absence of NaOH) and NaDCC (in the presence of NaOH only) produced degradation of spore coat and cortex material which may be related to their rapid sporicidal action at low concentrations under these conditions. By contrast, chloramine-T produced no degradation of cortex peptidoglycan and was only effective against normal and alkali-treated spores at high concentrations, requiring extraction of peptidoglycan with urea/dithiothreitol/sodium lauryl sulphate (UDS) or UDS/lysozyme to achieve significant activity at low concentrations. Results suggest that the sporicidal action of CRAs is associated with spore coat and cortex degradation causing rehydration of the protoplast allowing diffusion to the site of action on the underlying protoplast.

Bacterial spores and chemical sporicidal agents

Bacterial spores are among the most resistant of all living cells to biocides, although the response depends on the stage of sporulation. The development of resistance to some agents such as chlorhexidine occurs much earlier in sporulation than does resistance to glutaraldehyde, which is a very late event. During germination or outgrowth or both, resistance is lost and the cells become as susceptible to biocides as nonsporulating bacteria. Mechanisms of spore resistance to, and the action of, biocides are discussed, and possible means of enhancing antispore activity are considered. The clinical and other uses of sporicidal and sporostatic chemical agents are described.

Death, injury and revival of chemically treated Bacillus subtilis spores

The resistance of spores of Bacillus subtilis NCTC 10073 to glutaraldehyde, sodium hypochlorite and povidone-iodine was compared. Revival of treated spores was examined by use of defined germination media and conditions, protein denaturing agents, ultrasonics and heat. Revival, obtained after treatment with each of the three chemical agents, originated under different sets of conditions and was of two recognizably distinct types. The results, including the evidence of electron microscopy, are discussed in terms of chemical-spore reactivity and the implications on their use and suitability as chemical sterilizers.

Studies on the bacterial spore coat. IX. The role of surface charge in germination of Bacillus megaterium spores

The surface charge of Bacillus megaterium QM B1551 spores was estimated to be negative, -0.2 ad -0.4 mueq/mg by colloidal titration using glycol chitosan (GCh) and methylglycol chitosan (MGCh), respectively, as positive colloids. MGCh, which reacts with all of the negatively charged groups including carboxylate, inhibited the second stage of the germination to result in semirefractile spores, but GCh, which reacts only with strong acidic groups such as phosphate, did not. The spores produced in a medium with limited phosphate had coats with low phosphate content and carried less negative charge, and they were induced to germinate with 0.4 mM KNO3, which is one-tenth of the minimum concentration required for the germination of the control spores. A similar increase in germinability was observed in spores incubated with calcium acetate. The results suggest that the role of the surface charge in germination is as follows. Strong acidic groups (such as phosphate) in the coat may block the action of ionic germinants and act as a barrier against the initiation of ionic germination. Positively charged compounds (such as calcium) may compensate for this blocking effect. Weak acidic groups (such as carboxylate) may be involved in the later stage of germination.