sentence: The RNA helicase genes , crhC , csdA and deaD , whose expression is regulated by a reduction in growth temperature , have been characterized in the photosynthetic cyanobacterium Anabaena sp. strain PCC 7120 ( 8,9 ) , Escherichia coli ( 10 ) , and the cold-adapted Antarctic methanogenic archaeon , Methanococcoides burtonii ( 11 ) , respectively .