Prokaryótar

Prokaryótar, commonly called prokaryotes, are single-celled organisms characterized by the absence of a nucleus and other membrane-bound organelles. Their genetic material is typically a single circular chromosome located in a region of the cytoplasm called the nucleoid, and they often carry smaller DNA molecules known as plasmids. Prokaryotes have ribosomes of the 70S type and a cytoplasmic membrane that lies beneath a rigid cell wall. In bacteria the cell wall commonly contains peptidoglycan, whereas archaea have different cell wall compositions, such as pseudopeptidoglycan or other polymers.

Prokaryotes are divided into two domains: Bacteria and Archaea. A traditional older framework used the kingdom Monera, but modern taxonomy recognizes Bacteria and Archaea as separate domains. Prokaryotes are found in nearly every habitat on Earth, including soil, water, air, acidic or salty environments, and even extreme temperatures. They range in size from about 0.2 to several micrometers and exhibit diverse shapes, including cocci (spherical), bacilli (rod-shaped), and spirilla or spirochetes (spiral).

Metabolically, prokaryotes show remarkable diversity. They include photosynthetic cyanobacteria, chemolithoautotrophs, and chemoorganotrophs. Some are aerobic, others anaerobic, and some can use a wide range of energy sources. Reproduction is mainly asexual via binary fission, though horizontal gene transfer through transformation, transduction, and conjugation spreads genetic material.

Ecologically, prokaryotes drive nutrient cycling, decompose organic matter, fix nitrogen, and form mutualistic relationships with plants and animals. They also include pathogens and symbionts. In biotechnology, prokaryotes underpin processes such as fermentation, antibiotic production, and modern gene editing tools like CRISPR.