Submitted to: Archives of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2005
Publication Date: 3/15/2005
Citation: Flythe, M.D., Russell, J.B. 2005. The ability of acidic ph, growth inhibitors and glucose to increase the proton motive force and energy spilling of amino acid-fermenting clostridium sporogenes md1 cultures. Archives Of Microbiology. 183:236-242.
Interpretive Summary: American cattle consume over 150 million tons of fermented plant materials (silage) each year. However, silages are frequently contaminated with clostridia. Clostridia ferment amino acids, produce ammonia and increase silage pH. If the silage pH increases, molds and other toxic microorganisms proliferate. Amino acid fermenting clostridia were isolated from fresh alfalfa, fresh corn, and silages, and all of them could ferment amino acids at acidic pH values. Our experiments indicated that the clostridia took up amino acids, produced ammonia and grew even if they did not have a membrane potential. Research on silage microbiology has the potential to decrease the cost of American cattle production and protect cattle and consumers from potentially toxic bacteria.
Technical Abstract: Clostridium sporogenes MD1 grew rapidly with peptides and amino acids as an energy source at pH 6.7. However, protonmotive force was only -25 mV, and protonophores did not inhibit growth. When extracellular pH was decreased with HCl, the chemical gradient of protons and the electrical membrane potential increased. The protonmotive force was -125 mV at pH 4.7, even though growth was not observed. At pH 6.7, glucose addition did not cause an increase in growth rate, but membrane potential increased to -70 mV. Protein synthesis inhibitors also significantly increased membrane potential. Non-growing, arginine-energized cells had a membrane potential of -80 mV at pH 6.7 or 4.7, but membrane potential was not detected if the F1FO ATPase was inhibited. Arginine-energized cells initiated growth if other amino acids were added at pH 6.7, and membrane potential and ATP declined. At pH 4.7, ATP production remained high. However, growth could not be initiated, and neither membrane potential nor the intracellular ATP concentration declined. Based on these results it appears that C. sporogenes MD1 does not need a large protonmotive force to grow, and protonmotive force appears to serve as a mechanism of ATP dissipation or energy spilling.