Peculiarities of diurnal vertical migrations of zooplankton in polar seas

Studies of diurnal vertical migration in the polar seas are of special interest since we arc able to make observations in nature (without the possible drawbacks of laboratory experiments) of the behavior of animals under the widely varying light conditions that prevail during different seasons. Thus, during the polar summer it is possible to investigate the diurnal migration under conditions of uninterrupted daylight, during the polar autumn and spring under changing conditions of alternating days and nights, and finally in winter under conditions of permanent darkness. At present a series of special diurnal stations are available, taken mainly in the Barents Sea, as well as in the White Sea. Unfortunately, owing to weather conditions, no diurnal stations have been obtained as yet in winter and spring

Heterologous Expression of Alteromonas macleodii and Thiocapsa roseopersicina [NiFe] Hydrogenases in Synechococcus elongatus

Oxygen-tolerant [NiFe] hydrogenases may be used in future photobiological hydrogen production systems once the enzymes can be heterologously expressed in host organisms of interest. To achieve heterologous expression of [NiFe] hydrogenases in cyanobacteria, the two hydrogenase structural genes from Alteromonas macleodii Deep ecotype (AltDE), hynS and hynL, along with the surrounding genes in the gene operon of HynSL were cloned in a vector with an IPTG-inducible promoter and introduced into Synechococcus elongatus PCC7942. The hydrogenase protein was expressed at the correct size upon induction with IPTG. The heterologously-expressed HynSL hydrogenase was active when tested by in vitro H2 evolution assay, indicating the correct assembly of the catalytic center in the cyanobacterial host. Using a similar expression system, the hydrogenase structural genes from Thiocapsa roseopersicina (hynSL) and the entire set of known accessory genes were transferred to S. elongatus. A protein of the correct size was expressed but had no activity. However, when the 11 accessory genes from AltDE were co-expressed with hynSL, the T. roseopersicina hydrogenase was found to be active by in vitro assay. This is the first report of active, heterologously-expressed [NiFe] hydrogenases in cyanobacteria