FIG 2.

Methane and formate produced by Prochlorococcus strain MIT9301 grown with phosphate, phosphite, methylphosphonate (MPn), or hydroxymethylphosphonate (HMPn). (A) Dissolved methane concentrations measured in MIT9301 cultures after 7 days of growth in gas-tight bottles. The control measurement corresponds to the methane concentration at the start of the incubation to account for the solubility of atmospheric methane in the medium. The error bars represent the standard deviations of the means from triplicate cultures. (B) Formate concentrations measured in the supernatant of MIT9301 cultures grown to maximum cell densities for 14 days with the indicated P substrate as sole P source. Formate was not detected in the sterile medium at the start of the incubation. Error bars represent the standard deviations of the means from triplicate cultures. The average formate concentrations in treatments marked with the same lowercase letter (a, b, c, or d) were significantly different (P < 0.05).