Daren Molina (UTPA) and F.A. Rainey, Biological Sciences

Survival of Soil Bacterial Communities Following Desiccation

The Atacama Desert is located in northern Chile and Southern Peru along the Pacific coast. This desert has been called the driest place in the earth. According to previous studies, there is almost no detectable trace of bacteria in the soil of the hyper-arid core region of the desert around 24º and 25º S. The soil bacterial counts increase to the south along the precipitation gradient. It was hypothesized that there would be a reduction in the colony forming units (cfu’s) of the soil bacteria if samples from the moister region of the desert were desiccated. Soil samples from three regions in the desert (AT05 176 – Altamira, AT05 177 – Brad’s Site, AT05 22 – Vineyard) and a Baton Rouge cornfield (CF05) were tested. Soil from each site was placed in separate Petri dishes and place inside a Secador Desiccator along with an amount of silica gel and allowed to dry. There were four replications of each sample placed in four desiccators. One desiccator was opened per week for the next four weeks and plated out on marine agar and 1/10 plate count agar (PCA). The impregnated plates were incubated at 28° for approximately 20 days and the counts were then analyzed for any trends and compared to a control. Humidity reading were taken of the four desiccators as well as the desert itself and then compared graphically. Desiccation appeared to have somewhat of an initial effect on the sites such as 1/10 PCA AT05 22. Less of a drop in CFU’s was determined in 1/10 PCA AT05 177 and MA CF05. Desiccation did not appear to affect the cornfield site more than the desert sites. The data gathered will have to be further analyzed via PCR, DNA sequencing and organism identification to determine the types and quantities of organisms in the soil for comparison purposes.