Science Buddies: "Ask an Expert"

Hi, I am in the Science Research program at my school, and I was directed to ask questions here. I am just beginning my research project, which involves inoculating soil with microbacteria. The main purpose of this process is to prevent and limit liquefaction, the sudden loss of shear strength and integrity in soil due to loss of friction between soil particles. This loss in strength happens when stress or loading causes water in the soil to distribute among the soil particles. The bacteria will help stabilize the soil by plugging the pores through which groundwater flows, combating the root cause of liquefaction.

One of my questions is regarding the species of microbacteria that would be viable for this type of experiment. An important criteria is that the bacterium must be small enough to clog the pores in the soil, close to around .1 nanometers^3 (http://www.urop.uci.edu/grants/sample_p ... ng%203.pdf). So far, I have only found Flavobacterium Johnsoniae as a possible species, but I haven't found a way to confirm this or to find other possible species.

My other question is regarding the process of inoculating the bacteria into the soil. I read a proposal for a similar project which indicated that the process of inoculation would simply involve placing the bacterial biofilms in the sample soil column and agitating the soil sample to even distribute the bacteria. I have no idea as to the validity of that procedure, and I was hoping you could share some knowledge on that?

Thank you for your time and help.

Hi,

I did some web surfing on your topic and found the same site you cited plus these others that look somewhat relevant. I saw at least four other bacteria in these sited as forming potentially useful biofims. The more frequently cited mechanism for soil stabilization was not mechanical clogging of soil structure pores by bacteria, but rather secretion of polymers out of the cells (exopolymers) that gelled the soil or rock grains into a more stable structure. I saw discussion about the influence of the chemical composition and physical size of the soil components on the nature of the biofilm developed, and the speed of development. You may want to think about these issues as they affect your study, and possibly try to develop working relationships with groups studying these issues. Here are some links that are of possible interest:

http://www.springerlink.com/content/r4417v7245q0n82h/

http://www.biofilm.montana.edu/files/CB ... sTAC08.pdf

http://onlinelibrary.wiley.com/doi/10.1 ... x/abstract

http://www.iuss.org/19th%20WCSS/symposium/pdf/1820.pdf

This looks like a very interesting area of research. Have fun with it!

Best regards,

Barrett L Tomlinson

Thanks for your help, Mr. Tomlinson. I've looked through the links you provided and gained some valuable information.

I've decided to modify my research project. The main focus of my experiement now is to determine how soil acidity affects the deposition of calcium carbonate by bacillus pasteurii. This deposition reaction solidifies the sand grains in a soil sample. My main problem now is determining a scientifically sound method of altering the pH level of a soil sample which will have a negligable effect upon the bacillus pasteurii. There is, of course, the classic adding of aluminums and irons to raise pH and adding of nitrates, etc. to lower the pH. However, I'm not sure if these methods will skew the results of my experiment. Can anyone provide some suggestions or links? Thank you.