- SAR11 is a clade of marine bacteria that are the most abundant heterotrophs in ocean surface water. They play a significant role in marine carbon cycling. Although many culturing experiments have been done on SAR11, there was no research that focused on verifying the observations about inhibition of SAR11 growth by organic compounds. I compiled a growth nutrient profile for future reference. The experiment reported here used a prototype strain of SAR11, Pelagibacter sp. HTCC7211 (HTCC7211), to verify the effect of the 12 selected compounds at varying concentrations on the growth of HTCC7211. HTCC7211 was grown on a defined artificial seawater (ASW) containing inorganic and organic nutrients, vitamins, methionine, glycine, and pyruvate. In addition to the ASW medium, each selected compound was added to the ASW at varying concentrations. I compared the specific growth rates of each treatment and reported here the effects of each treatment on the growth of HTCC7211. The specific growth rates of HTCC7211 under organic acid and osmolyte treatments are highest at medium concentrations. The patterns of HTCC7211 growth rates under amino acid treatments are complicated. The limitations of this experiment include no duplicates or triplicates for control group and treatment groups, slow doubling time of HTCC7211, and low pH value of the cultures. The findings of this experiment require further investigations; however, the
results still serve as a foundation or reference for future culturing experiments and the emerging metabolomic research that will help understand SAR11’s role in nutrient cycling in marine ecosystems.