What Criteria that can be used to classify microorganisms into groups?

Microorganisms can be classified based on criteria such as cell structure (prokaryotic or eukaryotic), shape (cocci, bacilli, spirilla), metabolic capabilities (aerobic or anaerobic), nutritional requirements (heterotrophic or autotrophic), and genetic composition (DNA or RNA-based). Additional classifications can include pathogenicity (disease-causing or non-pathogenic), ecological niche (soil, water, or air), and reproductive strategies (asexual or sexual).