title: A newly isolated Chlorella sp. from desert sand crusts exhibits a unique resistance to excess light intensity.
abstract: We recently isolated a small green alga from a biological sand crust (BSC) in the NW Negev, Israel. Based on its 18S rRNA and rbcL genes, it is a close relative of Chlorella sorokiniana and of certain strains of C. vulgaris and C. variabilis, but differs substantially in many aspects from C. sorokiniana. Because the classification of Chlorellales is still not resolved, we designated this species as C. ohadii (Trebouxiophyceae) in honor of Professor Itzhak Ohad. Under controlled laboratory conditions, C. ohadii showed marked structural and photosynthetic performance changes, depending on the carbon source used during growth, as well as remarkable resistance to photoinhibition. CO2 -dependent O2 evolution was not affected even when exposed to a light intensity of 3500 μmole photons m(-2)  s(-1) , over 1.5 times the maximal intensity reached at the BSC surface, whereas the variable fluorescence declined sharply. We briefly discuss the use of fluorescence to assess photosynthetic rate and the implications of this finding for the assessment of global BSCs activity.
authors.affiliation: Department of Plant and Environmental Sciences, Edmond J. Safra Campus - Givat Ram, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Haim
authors.initials: H
authors.lastname: Treves
authors.forename: Hagai
authors.initials: H
authors.lastname: Raanan
authors.forename: Omri M
authors.initials: OM
authors.lastname: Finkel
authors.forename: Simon M
authors.initials: SM
authors.lastname: Berkowicz
authors.forename: Nir
authors.initials: N
authors.lastname: Keren
authors.forename: Yoram
authors.initials: Y
authors.lastname: Shotland
authors.forename: Aaron
authors.initials: A
authors.lastname: Kaplan
mesh_terms: D002708:Chlorella / Q000145:classification* / Q000166:cytology / Q000302:isolation & purification* / Q000502:physiology; D000460:Chlorophyta; D003889:Desert Climate; D007557:Israel; D008027:Light; D010788:Photosynthesis; D010802:Phylogeny; D012822:Silicon Dioxide
chemical_list: D012822:Silicon Dioxide
keywords: CO2 concentrating mechanism; light intensity; photosynthesis; productivity