One Plate-double Nutrient Endospore Activation Method

Background

Thermophilic endospores (thermospores) are resistant structures. Thermospore represents resting phase/form of thermophilic bacteria which has the ability to survive under adverse conditions over a long time period and revive after arrival of favorable conditions. According to the thermophilic nature of these Bacilli, these spores are named “thermospores”. Thermophilic bacteria Gram-positive and few Gram-negative would initiate process of formation of endospores upon onset of adverse conditions such as high or low temperature, salt, nutrients, water activity, oxic and anoxic conditions. Thermospore can survive in natural harsh environment (hot springs, hydrothermal areas, acid mines, alkaline lakes, salt lakes, ocean waters and sun-heated soils) and artificial extreme environments (xenobiotic environments, dumping sites, heaters, geysers, compost piles and dry areas). According to the growth temperature, microorganisms can be classified into psychrophiles, mesophiles, thermophiles, extreme thermophiles and hyperthermophiles. Temperature is a prime factor for the growth and development of thermophilic Gram-positive Bacilli and Gram-negative Sporomusa spp.


Figure 1. Typical endospore of bacteria

Experimental evidence shows that at non-optimal conditions thermophilic Bacilli have different adaption strategies. Whereas non-sporulating bacteria can produce solutes and heat shock protein for their survival. However, thermophilic bacteria and/or thermospore fail to revive after long-term preservation of without sub-culture longer than a month period. This gives a clue that revival of endospore requires optimum growth conditions which may differ than optimum growth parameter for exponentially growing cell. The revival of such dormant endospores at low temperature was primarily explored in the early 1980s by Harold F. Foerster (Foerster, 1983). He has proposed how to activate and re-grow endospore from Bacillus spp. In this protocol, we propose a modified procedure which consumes only one plate with double concentration of nutrients and applicable for thermophiles. This standardized protocol can be employed for the activation of mesophilic bacterial endospores. Moreover, we propose a specific incubation condition and simple protocol for activation of dormant. This is a tribute to Harold F. Foerster (1983).