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
Bacteria have well-developed cell structure despite their simplicity. Typical bacterial shapes include coccus, bacillus, coccobacillus, spiral, and filamentous. Bacterial cells are small, averaging 2 μm long and 0.5 μm in diameter. Cell envelope consists of cell membrane and cell wall
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
Molds are fungal structures formed by spores containing secondary metabolites. They consist of interconnected hyphae forming a mycelium network. Not all fungi form molds, some grow as single cells. Molds require moisture for growth and can survive extreme conditions
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
Genus contains about 150 species of unicellular flagellates. Found in freshwater, seawater, and snow as "snow algae". Name comes from Greek "chlamys" (cloak) and "monas" (solitary)