Microbiology emerged from Pasteur and Koch's bacterial research in late 1800s. Bacteria are prokaryotic single-celled organisms without membrane-bound nucleus. Woese's 1977 discovery divided bacteria into eubacteria, archaea, and eukarya. Bacteria range in width from 0.5 to 5 micrometres and can be shaped like spheres. Archaea lack peptidoglycan in cell walls and can survive extreme environments
Organisms are classified into three domains and six kingdoms. Classification based on cell type, nutrient acquisition, and reproduction. Modern classifications use cladistics, noting kingdoms aren't monophyletic
Ciliates are hair-like organelles used for swimming, feeding, and sensing. About 4,500 free-living species exist, with potential 27,000-40,000 extant species. Range in size from 10 μm to 4 mm in length. Found in water environments including lakes, oceans, and soils
Gram stain was developed by Hans Christian Gram in 1884. Technique classifies bacteria into gram-positive and gram-negative groups. Named after Gram, who worked with Carl Friedländer in Berlin morgue
Mesothelium is a simple squamous epithelial cell layer derived from embryonic mesoderm. Forms lining of pleura, peritoneum, and pericardium. Covers internal organs as visceral mesothelium and surrounding body walls as parietal mesothelium. Surrounds male testis as tunica vaginalis
Hypha is a long, branching filamentous structure of fungi. Consists of cells surrounded by tubular cell wall. Divided into cells by internal cross-walls called septa. Average diameter of 4-6 μm