Light Organ example essay topic
413 words
Nyholm and Mcfall-Ngai. 1998. Sampling the Light-Organ Micro environment of Euprymna sco lopes: Description of a Population of Host Cells in Association with the Bacterial Symbiont Vibrio. Biol. Bull. 195: 89-97 Upon collecting a species of squid, Euprymna sco lopes, from the coast of Oahu, Hawaii, it was revealed that a light organ contained near its mandible is host to a bio luminescent bacteria, Vibrio. These light-organ crypts have lateral pores that expel a dense matrix consisting of live and dead host cells with the bacterial cells often adhered to their surface, in response to exposure to a light cue, which in its natural seawater habitat would occur every day at dawn. This study (Nyholm and Mcfall-Ngai, 1998), examines this die rhythm in terms of the cycle and the contents of the matrix in the light-organ of E. sco lopes, "including aspects of nutrient exchange, host immune response, and the control of symbiont number" (Nyholm and Mcfall-Ngai, 1998). Under a natural 12 hour dark 12 hour light cycle, the animals were anesthetized in ethanol and the light-organ was exposed to a light source and after staining the host cells, the exuded material was collected (lack of a light stimulus produced no venting). However, the matrix obtained from the organ was prepared for observance under scanning and transmission microscopy at different time intervals in the cycle. From this it was determined that levels of the bacteria are highest before dawn and drops to level of 5 to 10% just after venting, indicating that the purpose is removal of the bacteria from the organ. Some of the E. sco lope cells in the exudate contained acidic lysosomes, and "spaces of intact light organs occasionally contained intracellular bacteria... and many of the cells appeared to be undergoing degradation" (Nyholm and Mcfall-Ngai, 1998).
Along with the active cells of E. sco lope, many are also dead or non-functional, in fact microscopy revealed that around half of them had compromised membranes. Also, a mixture of membrane material and other constituents can be found, however, "To date, only one constituent has been defined, i. e., the host derived amino acids that supply the growing symbiont population with these metabolic building blocks" (Nyholm and Mcfall-Ngai, 1998). The future research of this relationship is concerned with determining specifics of cycle, the growth rate of the bacteria, and the identification of the other constituents contained in the matrix..
