NOVELTY - Generating (M1) hydrogen gas involves: a) propagating photosynthetic algae in a propagation medium comprising sulfur; b) co-culturing the algae with bacteria in a culturing medium for a length of time to ensure reduced oxygen culturing conditions; c) depleting the bacteria in the culturing medium to generate a bacteria-reduced culturing medium; d) culturing the algae for a length of time sufficient to ensure anaerobic culturing conditions; e) culturing the algae in the culturing medium under anaerobic culturing conditions, to generate the hydrogen gas; and f) collecting the hydrogen gas.    USE - For generating hydrogen gas (claimed).    ADVANTAGE - The method allows for more rapid hydrogen gas photoproduction by the cultured algae, and in greater amounts, compared with a similar culture of algae cultured without added bacteria; and shorten the latency period between sulfur deprivation and establishment of microoxic and anaerobic conditions for hydrogen generation by the algae.    DETAILED DESCRIPTION - Generating (M1) hydrogen gas involves: a) propagating photosynthetic algae in a propagation medium comprising sulfur; b) co-culturing the algae with bacteria in a culturing medium for a length of time sufficient to ensure reduced oxygen culturing conditions, where the culturing medium comprises a reduced amount of sulfur compared to the propagation medium; c) depleting at least some of the bacteria in the culturing medium to generate a bacteria-reduced culturing medium; d) culturing the algae in the culturing medium for a length of time sufficient to ensure anaerobic culturing conditions; e) culturing the algae in the culturing medium under anaerobic culturing conditions, to generate the hydrogen gas; and f) collecting the hydrogen gas. INDEPENDENT CLAIMS are included for the following:    (1) generating (M2) hydrogen gas involving: a') propagating photosynthetic algae in a propagation medium comprising sulfur; b') culturing the algae in a culturing medium which comprises a reduced amount of sulfur compared to the propagation medium, for a length of time sufficient to establish anaerobic culturing conditions, where the culturing is co-culture with added bacteria for at least a portion of the length of time; c') culturing the algae in the culturing medium under anaerobic culturing conditions to generate the hydrogen gas; and d') collecting the hydrogen gas, where the length of time to anaerobic culture conditions of step (b') is reduced compared to the length of time of a similar culture of algae not co-cultured with added bacteria; and    (2) a system for generating hydrogen gas comprising a sealed culture vessel containing photosynthetic algae and bacteria co-cultured in a culturing medium having a reduced amount of sulfur as compared to an algal propagation medium; a source of illumination of the culture vessel; and a unit for collecting hydrogen gas from the culture vessel, where the bacteria are comprised in a bacterial containment in fluid association with an algae containment, where the algae containment is separated from it by a fluid- and gas-permeable and bacterial impermeable barrier.