bacily

Bacily refers to bacilli, the plural of bacillus, or more generally to any rod-shaped bacterium. In modern English, the standard plural is bacilli, while bacily appears mainly in historical texts or as a transliteration in other languages. The term derives from Latin bacillus, meaning "little staff."

Bacilli are a morphological category rather than a single taxonomic group. They are typically rod-shaped, about 0.3 to several micrometers long. Some are Gram-positive and spore-forming, notably the genus Bacillus (for example, Bacillus anthracis and Bacillus cereus). Other bacilli are Gram-positive but non-spore-forming (Listeria). Gram-negative bacilli include diverse genera such as Escherichia, Salmonella, and Pseudomonas. The group thus encompasses a broad range of physiological traits and ecological roles.

Ecology and distribution: Bacilli are widespread in soil, water, and on and within living organisms. They can act as environmental decomposers, mutualists, or part of normal microbiota. Some species are opportunistic pathogens, while others have no known impact on health.

Medical and industrial relevance: Several bacilli are notable for human disease, including Bacillus anthracis (anthrax) and Bacillus cereus (food poisoning). Others have beneficial applications, such as Bacillus subtilis in biotechnology and Bacillus thuringiensis, used as a biological pesticide. Because bacilli cover a broad spectrum of organisms, their study informs fields from ecology to medicine and industry.

See also: Bacillus, bacilli, Gram staining.