gramdodatnie

Gramdodatnie, often rendered as Gram-dodatnie in Polish, refers to the group of Gram-positive bacteria. In the standard Gram stain used in microbiology, Gram-positive organisms retain the crystal violet-iodine complex and appear purple under light microscopy, unlike Gram-negative bacteria which take up a counterstain and appear pink. This staining pattern reflects fundamental differences in cell wall architecture.

The defining characteristic of Gram-positive bacteria is a thick layer of peptidoglycan in the cell wall, which is rich in teichoic and lipoteichoic acids. This structure provides rigidity and affects interactions with the environment and antibiotics. Unlike many Gram-negative bacteria, Gram-positive species typically lack an outer membrane, though some have capsules or surface proteins that influence virulence and immune recognition. Exceptions exist: certain bacteria such as Mycobacterium and Nocardia have complex cell envelopes with mycolic acids and can be weakly Gram-positive or require special staining methods (acid-fast staining) for reliable visualization.

Taxonomically, Gram-positive bacteria encompass diverse phyla, notably Firmicutes (for example Staphylococcus, Streptococcus, Bacillus, and Clostridium) and Actinobacteria (including Mycobacterium and Corynebacterium). They include many clinically important pathogens as well as beneficial species in fermentation, biotechnology, and agriculture. Therapeutically, Gram-positive bacteria are generally susceptible to many beta-lactam antibiotics and glycopeptides, though resistance mechanisms such as beta-lactamases and altered targets are encountered in clinical settings.