Gramnegatiivisten

Gramnegatiivisten is Finnish terminology referring to Gram-negative bacteria, defined by their cell envelope and staining properties. The term appears in phrases such as gramnegatiivisten bakteerien tunnistus or gramnegatiivisten infektioiden aiheuttajat. In microbiology, the adjective describes a large and diverse group whose name derives from the Gram stain reaction.

Structure and staining

Gram-negative bacteria possess a double membrane with a thin peptidoglycan layer located in the periplasmic space, enclosed by an outer membrane rich in lipopolysaccharide (LPS). This envelope differs from Gram-positive bacteria, which have a thicker peptidoglycan layer and no outer membrane. On the Gram stain, gramnegatiivisten organisms do not retain crystal violet and appear pink or red after counterstaining with safranin. The outer membrane and LPS contribute to their characteristic permeability and can trigger immune responses via lipid A, a component of LPS.

Taxonomy and ecology

The Gram-negative group includes many taxonomic lineages such as Proteobacteria, Bacteroidota and others. They populate diverse habitats and include numerous commensals and pathogens. Common human pathogens in this group are Escherichia coli, Salmonella, Neisseria meningitidis and Neisseria gonorrhoeae, Haemophilus influenzae, Pseudomonas aeruginosa, Legionella, Vibrio, Helicobacter and Campylobacter species. However, many gramnegatiivisten bacteria are harmless or beneficial, for example in the gut microbiota.

Clinical relevance

Traditionally, gramnegatiivisten infections are identified by Gram staining and culture, guiding antibiotic choice. Their outer membrane can limit antibiotic entry and confer intrinsic resistance; many species produce beta-lactamases or other resistance mechanisms, complicating treatment. Effective management relies on susceptibility testing and awareness of potential endotoxin release during severe infections.