title: Reduced growth of Blastocrithidia culicis and Crithidia oncopelti freed of intracellular symbiotes by chloramphenicol.
abstract: The intracellular symbiotes of Blastocrithidia culicis and Crithidia oncopelti can be eliminated from cultures of the flagellates by a single chloramphenicol (CAP) treatment. Effective dosages were determined to be 0.01-0.08 per cent (w/v) CAP after a treatment for 2 weeks or more for B. culicis and 0.08 per cent (w/v) after 1 month for C. oncopelti in most cases. Ineffective dosages only lowered the numbers of symbiote-bearing flagellates. Growth of both species of flagellates in the presence of CAP was reduced in proportion to the drug concentration. Repeated subcultures at effectie dosages yielded symbiote-free flagellates, which maintained a low level of growth rate. After repeated subcultures at ineffective dosages, the growth rate rose and the symbiote-bearing cells, initially very few, increases in number. The lowest effective dosages proved to be marginal, often producing symbiote-free cultures, but occasionally cultures with a few symbiote-bearing cells. After repeated subcultures at these drug concentrations, symbiote-containing cultures grew faster than the symbiote-free cultures. Hence, the symbiotic bacteria benefit the growth of their hosts, perhaps by supplying essential factors that are adequate even in a rich blood medium.
mesh_terms: D002701:Chloramphenicol / Q000494:pharmacology*; D003470:Culture Media; D056890:Eukaryota / Q000254:growth & development* / Q000382:microbiology / Q000648:ultrastructure; D012287:Rickettsiaceae / Q000187:drug effects* / Q000648:ultrastructure
chemical_list: D003470:Culture Media; D002701:Chloramphenicol