Mutant microorganisms and methods of making and using

1. A Thermotoga maritima strain comprising at least one mutation in the ATP-binding component of a maltose ABC transporter, wherein the ATP-binding component of the maltose ABC transporter comprises the amino acid sequence of SEQ ID NO:15 and at least one mutation selected from V233S or V233F, wherein the T. maritima strain overproduces molecular hydrogen (H 2 ) compared to a T. maritima strain lacking the at least one mutation.

2. The strain of claim 1 , wherein the strain overproduces acetate compared to a T. maritima strain lacking the at least one mutation.

3. The strain of claim 1 , wherein the strain produces little to no lactate.

4. The strain of claim 1 , wherein the strain further comprises SEQ ID NO:16 having a W229Stop mutation and a deletion of nucleic acid sequences encoding the amino acid sequence of SEQ ID NO:17 and the amino acid sequence of SEQ ID NO:18.

5. A method of increasing the yield of molecular hydrogen (H 2 ) produced by Thermotoga maritima in culture, comprising:

inactivating, transiently, the lactate dehydrogenase gene in the T. maritima using a selectable marker to produce an inactivated T. maritima;

passaging the inactivated T. maritima a plurality of times under selective pressure to produce a compensating T. maritima , wherein the compensating T. maritima comprises a compensating mutation;

screening the compensating T. maritima for an increase in H 2 ; and

selecting and isolating the compensating T. maritima having an increase in H 2 , wherein the compensating mutation is in the ATP-binding component of a maltose ABC transporter, wherein the ATP-binding component of the maltose ABC transporter comprises the amino acid sequence of SEQ ID NO:15 and at least one mutation selected from V233S or V233F.

6. The method of claim 5 , further comprising sequencing the compensating T. maritima.