Effect of carotenoid deficiency on cells and chlorosomes of Chlorobium phaeobacteroides

Citation
Jb. Arellano et al., Effect of carotenoid deficiency on cells and chlorosomes of Chlorobium phaeobacteroides, ARCH MICROB, 175(3), 2001, pp. 226-233
Citations number
49
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ARCHIVES OF MICROBIOLOGY
ISSN journal
0302-8933 → ACNP
Volume
175
Issue
3
Year of publication
2001
Pages
226 - 233
Database
ISI
SICI code
0302-8933(200103)175:3<226:EOCDOC>2.0.ZU;2-N
Abstract
The effects of inhibition of carotenoid biosynthesis by 2-hydroxybiphenyl o n the photosynthetic growth, pigment composition and chlorosome structure o f Chlorobium phaeobacteroides strain CL1401 were examined. At a concentrati on of 20 mug 2-hydroxybiphenyl.ml(-1), carotenoid synthesis was largely inh ibited (85%), but the photosynthetic growth rate was almost unaffected (mu (control)=0.00525+/-0.00007 h(-1) and mu (HBP-treated)=0.00505+/- 0.0005 h( -1)). Cells grown in the presence of the inhibitor were 5 mum-70 mum long, while control cells were between 2-5 mum long. Moreover, 2-hydroxybiphenyl- treated cells contained fewer, unevenly distributed chlorosomes per mum of cytoplasmic membrane with an irregular arrangement (2.5+/-1.5 vs of 9.1+/-1 .9). This was concomitant to the 83% decrease in the content of bacteriochl orophyll (BChl) e in 2-hydroxybiphenyl-treated cells. Electron microscopy r evealed that the shape of carotenoid-depleted chlorosomes changed from elli psoidal to spherical, although the mean volume was similar to that of contr ol chlorosomes. SDS-PAGE analysis of the chlorosome polypeptide composition showed that the amount of CsmA protein decreased by 60% in carotenoid-depl eted chlorosomes. This was paralleled by a decrease in the baseplate BChl a content. The data suggest that carotenoids are close to the chlorosomal ba seplate, where they carry out both structural and photoprotective functions .