NOVELTY - Methods for generating hydrogen gas using algae with reduced sulfate permease activity, are new. In some of the methods anaerobic bacteria are also used to produce more hydrogen.    USE - The methods are useful for generating hydrogen gas (claimed) for use as a fuel.    ADVANTAGE - Algae produce hydrogen gas in the absence of sulfur in their growth media, but removing sulfur from the growth media is problematic. The methods allow the production of hydrogen using algae without requiring the removal of sulfur from the media, and alleviate the need to allow the cells to go back to normal photosynthesis to recover metabolites such as starch and protein, allowing sustained and continuous hydrogen production. The methods including the use of green algae and photosynthetic purple bacteria are efficient in using a broad portion of the solar spectrum.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) generating (M1) hydrogen gas comprising:    (a) culturing algae under illumination in a media comprising sulfur, where the algae have reduced sulfate permease expression relative to wild-type;    (b) sealing the algae culture from atmospheric oxygen; and    (c) collecting hydrogen gas evolved;    (2) generating (M2) hydrogen gas comprising:    (a) subjecting a biomass comprising an algae to sunlight in a sulfur-containing media comprising carbon dioxide and inorganic nutrients under conditions that cause the algae to undergo oxygenic photosynthesis and to generate hydrogen gas; and    (b) subjecting an anaerobic photosynthetic bacterium in the media to sunlight under conditions so as to generate hydrogen from a nitrogenase/hydrogenase enzymatic system in the media;    (3) generating (M3) hydrogen gas, comprising:    (a) providing in an aqueous media a genetically modified strain of Chlamydomonas reinhardtii;    (b) providing a strain of Rhodobacter sphaeroides photosynthetic bacteria;    (c) exposing the media to sunlight under conditions to allow for the generation of biomass and hydrogen;    (d) subjecting an anaerobic photosynthetic bacterium in the media to sunlight so as to generate hydrogen from a nitrogenase/hydrogenase enzymatic system in the media;    (e) providing a strain of Clostridium in the media; and    (f) inducing fermentation of the biomass in the media via Clostridium sp.;    (4) generating (M4) hydrogen comprising culturing a combination of sulP1 strain of Chlamydomonas reinhardtii and Rhodobacter sphaeroides with Clostridium sp.;    (5) generating (M5) hydrogen gas, comprising:    (a) providing in an aqueous media a sulP1 strain of Chlamydomonas reinhardtii and Rhodobacter sphaeroides bacteria; and    (b) exposing the media to sunlight under conditions that allow the generation of hydrogen;    (6) an isolated nucleotide sequence selected from SEQ ID NOs 2-6 (3873, 1984, 1863, 2253, and 1853 bp) and a sequence which hybridizes to any one of them;    (7) an isolated amino acid sequence selected from SEQ ID NO:1 (411 amino acids) and a sequence with 90% or more sequence homology to SEQ ID NO:1;    (8) a genetically modified algae in which the sulfate uptake pathway is downregulated to 50% or less relative to wild-type algae;    (9) a composition comprising water, algae growth nutrients, and the algae of (8);    (10) an assay for detecting low levels of sulfur uptake in a sample of genetically modified green algae comprising:    (a) culturing a genetically modified sample of green algae in TAP media in lighted, anaerobic conditions;    (b) transferring an aliquot of the sample into a media comprising sulfur;    (c) culturing the aliquot in lighted conditions; and    (d) detecting the level of aryl-sulfatase (ARS) activity in the aliquot, where an elevated level of ARS activity is a positive indicator that the modified algae is deficient in sulfur uptake;    (11) an isolated antisense oligonucleotide comprising a nucleotide sequence complementary to (codons 118-412 of) SEQ ID NO:2;    (12) an expression vector comprising an antisense sequence complementary to codons 118-412 of SEQ ID NO:2; and    (13) a composition comprising a sulP strain of Chlamydomonas reinhardtii and a Rhodobacter sphaeroides bacterium that is anaerobic and photosynthetic.