bacilli

Bacilli
Bacillus subtilis, Gram stained
Scientific classification
Kingdom: Eubacteria Division: Firmicutes Class: Bacilli
Orders
Bacillales Lactobacillales

Bacilli specifically refers to a taxonomic class of bacteria. It includes two orders, Bacillales and Lactobacillales, which contain several well-known pathogens like Bacillus anthracis (the cause of anthrax), Streptococcus, and Staphylococcus. All members of Class Bacilli are gram-positive.

Word Ambiguity

There are several related concepts that make use of similar words, and the ambiguity can create considerable confusion. The term "Bacillus" (capitalized and italicized) is also the name of a genus that, among many other genera, falls within the Class Bacilli.

Also, "bacillus" (or the plural "bacilli") can be a generic term to describes the morphology of any rod-shaped bacterium. This general term does not mean that the subject is a member of the class or genus that has a similar name. Thus, the two do not necessarily have a similar group of characteristics. Not all members of Class Bacilli are rod-shaped (Staphylococcus is not), and many other rod-shaped bacteria exist that do not fall within that class. Morevoer, the general term "bacillus" does not necessarily indicate the Gram-positive staining common to Class Bacilli. For example E. coli is a Gram-negative, rod-shaped bacteria that could be described as "a Gram-negative bacillus". Some microbiologists have forsaken the general "bacillus" term because of the confusion it can create.

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