Inactivation of photosynthetic electron flow during desiccation of desert biological sand crusts and Microcoleus sp.-enriched isolates

Itzhak Ohad, Reinat Nevo, Vlad Brumfeld, Ziv Reich, Tom Tsur, Michael Yair, Aaron Kaplan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Filamentous cyanobacteria, the main primary producers in biological sand crusts, survive harsh environmental conditions including diurnal desiccation/rehydration cycles. Here we describe the inactivation of photosystem II during dehydration of native crusts (NC) and Microcoleus sp. isolates grown on nitrocellulose filters (NCF). The morphology of NCF cells, visualized by scanning-transmission and atomic-force microscopy, disclosed long bacterial filaments encapsulated in extracellular polysaccharides (EPS) tubes consisting of parallel fibrils (100–400 nm wide and 50–100 nm high) oriented mostly perpendicular to the tube length. Presence of empty EPS tubes indicated a gliding capability of the cells. Desiccation of NC resulted in a rapid decline of Fo and complete loss of Fv. These changes were accompanied by a decrease of 77 K PSII fluorescence emission relative to that of PSI, when excited at 430 nm, and a significant decrease of energy transfer from phycobilisomes to PSII. Lowering the turgor pressure through the addition of 1.5 M trehalose to natural crusts, reduced Fv/Fm by over 50% and was accompanied by a decrease of 77 K PSI fluorescence induced by chlorophyll excitation. Excitation of phycobilisomes resulted in a downshift of the PSI emission wavelength by 8 nm, indicative of reduced energy transfer from LHCI to the core PSI. Decline of Fv/Fm in trehalose-incubated NCF cells did not induce significant changes in 77 K fluorescence emission. These results suggest that alterations in energy transfer from antennae to reaction centers may be part of the survival strategy of Microcoleus.

Original languageEnglish
Pages (from-to)977-982
Number of pages6
JournalPhotochemical and Photobiological Sciences
Volume4
Issue number12
DOIs
StatePublished - 23 Nov 2005

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