David A. Stahl, pp. Robert S. Burlage, pp. Molecular methods attempt to detect and identify bacteria based on individual molecules which are characteristic of specific bacteria, fungi, algae, etc. Species are defined by distinctness rather than by differences.
Species consist of populations rather than unconnected individuals.
Species are not defined by the fertility of individuals but by the reproductive isolation of populations. Species are reproductive communities of populations that occurpy a specific niche in nature. The species is an ecological unit that, regardless of the individuals composing it, interacts as a unit with other species with which it shares the environment. The species is a genetic unit, a gene pool, whereas the individual is a temporary vessel holding a portion of the gene pool for a short time. In bacteria a gene is a continuous stretch of DNA which encodes for a single function.