Document Detail

Symbiosis in Paramecium Bursaria.
MedLine Citation:
PMID:  785659     Owner:  NLM     Status:  MEDLINE    
Paramecium bursaria normally appears green dut to several hundred symbiotic Chlorella which are dispersed throughout its cytoplasm. The symbionts are situated within individual vacuoles and these alga-vacuole complexes grow and divide at a rate compatible with that of the paramecium. The symbiotic units also persist through conjugation and the subsequent reorganization of the host. Studies of the benefit of the symbiosis to the ciliate hosts have shown that they are able to grow and survive better than aposymbiotic animals in environments deficient in bacteria. The symbionts are also able to extract nourishment from the host when it is well fed and they are deprived of light. The biochemical nature of these exchanges has not been determined. Potential symbionts usually enter the host in food vacuoles. If they are ingested in sufficient numbers, they are able to interfere with the normal course of host digestion, perhaps by preventing the release of digestive enzymes into the food vacuole. All natural symbionts of P. bursaria appear able to reinfect aposymbiotic cells. Some freeliving strains of Chlorella and related algae are also infective, but these associations are relatively unstable and provide little evident benefit to the host. Host susceptibility to infection by certain strains of free-living algae is invariably lost with time. This loss is specific and often rapid, but it does not occur simultaneously in subcultures derived from the original susceptible culture. The basis for these susceptibility changes is still unknown, but they may be related to long-lasting effect of the previous symbionts on the digestive efficiency of the paramecium host.
M W Karakashian
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Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Symposia of the Society for Experimental Biology     Volume:  -     ISSN:  0081-1386     ISO Abbreviation:  Symp. Soc. Exp. Biol.     Publication Date:  1975  
Date Detail:
Created Date:  1976-10-29     Completed Date:  1976-10-29     Revised Date:  2000-12-18    
Medline Journal Info:
Nlm Unique ID:  0404517     Medline TA:  Symp Soc Exp Biol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  145-73     Citation Subset:  IM    
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MeSH Terms
Cell Division
Chlorella* / growth & development,  metabolism
Maltose / metabolism
Paramecium / growth & development,  microbiology,  physiology
Reproduction, Asexual
Species Specificity
Vacuoles / physiology
Reg. No./Substance:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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