Opsin three domains of life: Archaea, Bacteria, and Eukaryota. In Eukaryota, type I opsins are found mainly in unicellular organisms such as green algae, and in fungi. In most complex multicellular eukaryotes, type I opsins have been replaced with other light-sensitive molecules such as cryptochrome and phytochrome in plants, and type II opsins in Metazoa (animals). Microbial opsins are often known by the rhodopsin form of the molecule, i.e., rhodopsin (in the broad sense) = opsin + chromophore. Among the many kinds of microbial opsins are the proton pumps bacteriorhodopsin (BR) and xanthorhodopsin (xR), the chloride pump halorhodopsin (HR) the photosensors
Broad-spectrum antibiotic of antimicrobial resistance. An example of a commonly used broad-spectrum antibiotic is ampicillin. Broad-spectrum antibiotics are properly used in the following situations: Antibiotics are often grouped by their ability to act on different bacterial groups. Although bacteria are biologically classified using taxonomy, disease-causing bacteria have historically been classified by their microscopic appearance and chemical function. The morphology of the organism may be classified as cocci, diplococci, bacilli (also known as "rods"), spiral-shaped or pleomorphic. Additional classification occurs through the organism's ability to take up the Gram stain and counter-stain; bacteria that take up the crystal violet dye stain are referred