Gracilicutes

Gracilicutes is a taxonomic division of bacteria characterized by their Gram-negative cell wall structure. This defining feature means they do not retain the crystal violet stain during the Gram staining procedure, instead appearing pink or red. The cell wall of Gracilicutes is typically composed of a thin peptidoglycan layer situated between an inner cytoplasmic membrane and an outer membrane. This outer membrane contains lipopolysaccharides (LPS), which can play a role in the pathogenicity of some species. The term Gracilicutes, derived from Latin words meaning "slender" and "skin," reflects the relatively thin peptidoglycan layer compared to Gram-positive bacteria. This classification was historically significant in bacterial taxonomy, though modern phylogenetic approaches based on genetic sequencing have led to revisions in bacterial classification. However, the Gram stain characteristic remains a fundamental diagnostic tool in microbiology for initial bacterial identification. Examples of bacteria belonging to this group include many common and medically important species such as Escherichia coli, Salmonella, Pseudomonas, and Vibrio. Their diverse metabolic capabilities and ecological roles are extensive, contributing to various environments from soil and water to host organisms.