Effects of micronutrients on growth and starch hydrolysis of Thermococcus guaymasensis and Thermococcus aggregans.
The effects of micronutrients on growth of Thermococcus guaymasensis and Thenrmococcus aggregans in a starch-containing medium were investigated. A trace minerals solution, a vitamins solution and calcium chloride were omitted from the medium or added in different amounts. The growth rates of both species were not affected over a significant range of concentrations of these compounds, but appreciable inhibition of growth was observed after the addition of elemental sulfur to the medium. T. guaymasensis exhibited a significant tolerance to high amounts of trace element and vitamin solutions but growth was inhibited by the omission of these compounds from the medium. Moreover, both amylolytic and pullulytic activities increased in the presence of 6-fold higher amounts of trace element and vitamin solutions, compared to the concentrations used in the usual medium. In T. aggregans, both enzymatic activities were enhanced in the presence of either increased (4-fold) amounts of trace element and vitamin solutions, or after the addition of elemental sulfur to the medium. Furthermore, larger activities of starch-hydrolysing enzymes were detected with a 10-fold higher concentration of calcium chloride, compared to the usual medium, in the absence of trace element and vitamin solutions. When both Thermococcus species were tested for the tolerance to specific cations and oxyanions, T. guaymasensis exhibited higher tolerance compared to T. aggregans, the former strain being capable to grow in the presence of 6 mM Ni2+, 4mM Cu2+, 1.5 mM SeO4(2-), and 1.5 mM MoO4(2-). The content of total cell proteins followed the pattern of starch-hydrolysing enzymes and an over-expression of proteins in the range of 35, 50 and 70 kDa was observed.
Canganella
F
F
Department of Agrobiology and Agrochemistry, University of Tuscia, Viterbo, Italy. canganel@unitus.it
Kato
C
C
Horikoshi
K
K
D003470:Culture Media; D006868:Hydrolysis; D013213:Starch / Q000378:metabolism*; D019712:Thermococcus / Q000254:growth & development* / Q000378:metabolism; D014131:Trace Elements / Q000378:metabolism*; D014815:Vitamins / Q000378:metabolism*
D003470:Culture Media; D014131:Trace Elements; D014815:Vitamins; D013213:Starch