NOVELTY - Generating hydrogen gas comprising culturing algae under illuminated conditions in a media comprising sulfur, where the sulfate permease expression of the algae is reduced relative to normal wild-type algae, sealing the algae culture from atmospheric oxygen, and collecting evolved hydrogen gas, is new.    USE - The method is used for generating hydrogen gas (claimed).    ADVANTAGE - The inventive method includes culturing a medium, which is more closely aligned with naturally occurring media as compared to prior processes that require nutrient depletion from the media. It allows continuous production of hydrogen without having to restore viability to the algae in the culture after 80-100 hours.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (a) an assay for detecting low levels of sulfur uptake in a sample of genetically-modified green algae comprising culturing a genetically-modified sample of green algae in TAP media in lighted, anaerobic conditions, transferring an aliquot of the sample into a media comprising sulfur, culturing the aliquot in lighted conditions, and detecting the levels of aryl-sulfatase (ARS) activity in the aliquot in which the elevated level of ARS activity is a positive indicator that the genetically-modified green algae is deficient in sulfur uptake compared to a wild-type algae;    (b) an isolated nucleotide sequence comprising a fully defined sequence of 3840 base pairs (N1), or 1984 base pairs (N2), as given in the specification, or a sequence that hybridizes to N1 or N2;    (c) an isolated amino acid sequence comprising a fully defined 411 amino acid precursor protein (S1), as given in the specification, or sequence with 90 % or more sequence homology with S1;    (d) a genetically-modified algae in which the sulfate uptake pathway is down regulated to 50 % or less to a native, wild-type, unmodified algae;    (e) a composition comprising water, algae growth nutrients, algae genetically modified for sulfate permease expression, reduced by 50 % or more relative to an unmodified wild type version;    (f) an isolated antisense oligonucleotide sequence comprising a sequence complementary to (N1); and    (g) an isolated antisense oligonucleotide sequence comprising a sequence complementary to codons 118-412 of (N1);    (h) an expression vector comprising an isolated antisense oligonucleotide sequence comprising a sequence complementary to codons 118-412 of (N1); and    (i) an algae-containing composition comprising a sulPl strain of Chlamydomonas reinhardtii and Rhodobacter sphaeroides bacterium that is anaerobic and photosynthetic.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the pathway of sulfate uptake by the cell and chloroplast in Chlamydomonas reinhardtii and pointing to the role of sulfur-mediated protein synthesis on the activity of oxygen-producing photosynthesis.