Sucretolerance in oligosaline soils and halotolerant bacteria
AdvisorSchneegurt, Mark A.
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It is well established that microbial growth is decreased with the reduction of available water in a given environment. The availability of water is referred to as water activity and is expressed in aw values, that provide a reference measure between high-solute environments. Organisms that can survive in environments with low water activity are considered to be osmotolerant. There are many environments that have low water activity and extensive research has been done on organisms growing in these environments. However, most of the research has been done either with yeast in high-sugar environments or bacteria in high salt. Furthermore, the current planetary protection guidelines established by NASA were made using older sugar literature dealing with yeast. This was due to the assumption that water activity affects organisms similarly independent of the solute. Our current findings show that this assumption is invalid and that halotolerance does not confer sucretolerance. Therefore, one of the main objectives for this study was to look at the relationship between sugar and salt tolerance in bacteria. With regard to this objective it was hypothesized that bacterial growth responses would be different depending on the solute. Screening of salinotolerant bacteria in multiple high-solute media, supports the conclusion that there is a difference between high-solute environments in terms of microbial growth The second objective of the study was to look at the abundance of bacteria which can survive in high-solute environments. With regard to this objective, it was hypothesized that soil bacteria that can grow in high-sugar environments would be rare. Also those bacteria which could survive high-sugar environments also would display salinotolerance. Screening of soils in high-sugar media showed decreased growth, especially at saturation. Isolation of bacteria from the soils yielded primarily Bacillus species, that also displayed salinotolerance.
Thesis (M.S.)--Wichita State University, Fairmount College of Liberal Arts and Sciences, Dept. of Biological Sciences