Pattern of cyanophycin accumulation in nitrogen-fixing and non-nitrogen-fixing cyanobacteria

Li, H Sherman, DM Bao, SL Sherman, LA

H. Li et al., Pattern of cyanophycin accumulation in nitrogen-fixing and non-nitrogen-fixing cyanobacteria, ARCH MICROB, 176(1-2), 2001, pp. 9-18

38

INGLESE

Article

Microbiology

ARCHIVES OF MICROBIOLOGY

0302-8933 → ACNP

176

1-2

2001

9 - 18

ISI

0302-8933(200107)176:1-2<9:POCAIN>2.0.ZU;2-Y

The temporal and spatial accumulation of cyanophycin was studied in two uni cellular strains of cyanobacteria, the diazotrophic Cyanothece sp. strain A TCC 51142 and the non-diazotrophic Synechocystis sp. strain PCC 6803. Bioch emistry and electron microscopy were used to monitor the dynamics of cyanop hycin accumulation under nitrogen-sufficient and nitrogen-deficient conditi ons. In Cyanothece sp. ATCC 51142 grown under 12 h light/12 h dark nitrogen -fixing conditions, cyanophycin was temporally regulated relative to nitrog enase activity and accumulated in granules after nitrogenase activity comme nced. Cyanophycin granules reached a maximum after the peak of nitrogenase activity and eventually were utilized completely. Knock-out mutants were co nstructed in Synechocystis sp. PCC 6803 cphA and cphB genes to analyze the function of these genes and cyanophycin accumulation under nitrogen-deficie nt growth conditions. The mutants grew under such conditions, but needed to degrade phycobilisomes as a nitrogen reserve. Granules could be seen in so me wild-type cells after treatment with chloramphenicol, but were never fou nd in AcphA and,AcphB mutants. These results led to the conclusion that cya nophycin is temporally and spatially regulated in nitrogen-fixing strains s uch as Cyanothece sp. ATCC 51142 and represents a key nitrogen reserve in t hese organisms. However, cyanophycin appeared to play a less important role in the non-diazotrophic unicellular strains and phycobilisomes appeared to be the main nitrogen reserve.