MCB 3020C Lecture Notes - Lecture 26: Euprymna Scolopes, Gastrointestinal Tract, Aliivibrio
Document Summary
Microbial symbionts can be acquired from: environmental reservoir (horizonal transmission, parent (vertical or heritable transmission) Heritable symbionts of insects are obligate (lack a free-living replicative stage). Primary symbionts are required for the host to reproduce: restricted to bacteriome, bacterial cells are found in bacteriocytes. Secondary symbionts: not required for reproduction, not always present in every individual, can invade different cells and live extracellularly, must provide a benefit, nutritional, protection from environment, protection from pathogens. Some parasitic symbionts manipulate host"s reproductive tissue: rickettsia-infected white flies produce twice the number of offspring compared to uninfected flies, the sperm of wolbachia-infected males can sterilize uninfected females. Some insects exploit the metabolic potential of the symbiont. Primary symbionts exhibit extreme gene reduction: genome of insect symbiont, genome of related free-living bacteria, retain only genes needed for host fitness, lose catabolic genes, pathogens normally lose anabolic genes. Termites classified as higher or lower based on phylogeny.
