BACTERIAL SPORES II. A STUDY OF BACTERIAL SPORE GERMINATION IN RELATION TO ENVIRONMENT

Incorporating germination-induction into decontamination strategies for bacterial spores

Bacterial spores resist environmental extremes and protect key spore macromolecules until more supportive conditions arise. Spores germinate upon sensing specific molecules, such as nutrients. Germination is regulated by specialized mechanisms or structural features of the spore that limit contact with germinants and enzymes that regulate germination. Importantly, germination renders spores more susceptible to inactivating processes such as heat, desiccation, and ultraviolet radiation, to which they are normally refractory. Thus, germination can be intentionally induced through a process called germination-induction and subsequent treatment of these germinated spores with common disinfectants or gentle heat will inactivate them. However, while the principle of germination-induction has been shown effective in the laboratory, this strategy has not yet been fully implemented in real-word scenarios. Here, we briefly review the mechanisms of bacterial spore germination and discuss the evolution of germination-induction as a decontamination strategy. Finally, we examine progress towards implementing germination-induction in three contexts: biodefense, hospital settings and food manufacture.

SIGNIFICANCE AND IMPACT

This article reviews implementation of germination-induction as part of a decontamination strategy for the cleanup of bacterial spores. To our knowledge this is the first time that germination-induction studies have been reviewed in this context. This article will provide a resource which summarizes the mechanisms of germination in Clostridia and Bacillus species, challenges and successes in germination-induction, and potential areas where this strategy may be implemented.

264. The effect of variations in the fat percentage and in the reaction (pH) of milk media on the heat resistance of certain milk bacteria

1. A review of the literature shows that the destruction of living microorganisms by heat is a complex process, and that the problem is particularly difficult when it is applied to the heat resistance of spores.

2. The problems involved in the method of heating and in the choice of a container for the inoculated substrate for heat-resistance tests are discussed, with special reference to the difficulties encountered at high temperatures such as are used in studies with spores of aerobic bacteria. Four different types of containers, namely, (a) glass capillary tubes, (b) glass ampoules or bulbs, (c) glass Pasteur pipettes and (d) corked test tubes, have been tested, and the latter were found to fulfil the necessary requirements.

3. A trial test of the heat resistance was conducted on nearly forty strains of aerobic sporeformers isolated from canned milk products, in order to obtain general information regarding the difficulties which might be expected in later and more detailed studies. Many of the strains were found to be exceedingly heat resistant. No dormancy was apparent when the spores were heated and subsequently incubated in milk products. “Skips” were only observed to any great extent among strains ofB. licheniformis.

4. Special studies of the heat resistance of three strains ofB. subtiliswhich had produced bitterness and thinning in canned cream were made. Details are given of the methods of preparing spore suspensions for these tests and of preparing the substrates for subsequent inoculation in such a way that equal concentrations of spores are present in the final subsamples.

5. The effect of the reaction of the substrate on the destruction of two of these strains ofB. subtilisby heat has been examined, but over the narrow range of pH. tested the results, which have been expressed as survival percentages, lack consistency.

Stimulation of germination and respiration of the spores of Bacillus megatherium by manganese and monovalent anions

1. The addition of manganese in a concentration as low as 1.8 x 10(-5)M stimulates both respiration and germination markedly and eliminates the need for heat activation of spores respiring in inorganic salts-glucose. 2. Rapid germination and respiration of B. megatherium spores require a proper balance of ions in the nutrient medium. The repressive effect of a high phosphate concentration can be eliminated or balanced by chloride, or by other monovalent anions. Adenosine can relieve the necessity for chloride in such a system.