Endospores are hardy, defensive structures that enable some bacteria to survive harmful environmental conditions, such as starvation, high temperatures, desiccation (drying out), chemical disinfectants and extremes in pH.
Recursive formula is a formula that is used to determine the next term of a sequence using one or more of the preceding terms.
Certain sequences (not all) can be defined (expressed) in a recursive form. In a recursive formula, each term is defined as a function of its preceding term(s). [Each term is found by doing something to the term(s) immediately in front of that term.]