bakteriens

Bakterien, or bacteria, are single-celled prokaryotic microorganisms that lack a membrane-bound nucleus. They are among the oldest and most diverse life forms on Earth, found in virtually every habitat. Bacteria come in a variety of shapes, including spheres (cocci), rods (bacilli), and spirals (spirilla).

Most bacteria have cell walls containing peptidoglycan. They reproduce asexually by binary fission, allowing rapid population growth under favorable conditions, though some species form dormant endospores.

Bacteria exhibit diverse metabolisms. They can be autotrophs, obtaining energy from light or inorganic compounds, or heterotrophs, consuming organic compounds. Some are aerobic, others anaerobic, and a few are facultatively anaerobic, surviving with or without oxygen.

They play essential roles in ecosystems and industry: nutrient cycling, decomposition, nitrogen fixation, fermentation, and the production of vitamins. In association with hosts, many bacteria form microbiota that aid digestion and immune function. However, some species cause diseases in humans, animals, and plants.

Laboratory study distinguishes Gram-positive and Gram-negative bacteria based on cell wall properties using Gram staining. Model organisms such as Escherichia coli and Bacillus subtilis have been central to molecular biology.

Public health concerns include bacterial infections and antibiotic resistance, driven by misuse of antibiotics and horizontal gene transfer through mechanisms like conjugation and transformation. Control measures include vaccination, sanitation, proper antibiotic stewardship, and hygiene.

Taxonomy of bacteria remains complex; recent methods rely on genetic sequencing to delineate lineages. In German, the term Bakterien refers to these microorganisms.