Production of volatile organic compounds in the culture of marine α-proteobacteria

Abstract:

Volatile organic compounds (VOCs) release halogens in the troposphere and in the stratosphere by photolysis and released halogens catalyze ozone depletion . In the ocean, macroalgae, phytoplankton, and bacteria are considered to be the main producers of VOCs. Recent investigations have shown that marine bacteria produce halomethanes such as chloromethane, bromomethane, and iodomethane. However, knowledge of aquatic VOC production, particularly through bacteria, is lacking. We studied the production of VOCs, including halomethanes, through the bacterium HKF-1. HKF-1 was isolated from brackish water in Sanaru Lake, Shizuoka prefecture, Japan. The bacterium belongs to the α-proteobacteria. Bacteria were incubated in marine broth 2216 (Difco) added with KI and KIO₃ (each at 0.02 μmol/L) at 25°C. VOCs in the gas phase above the cultured samples was determined using a dynamic headspace (GESTEL DHS)—gas chromatograph (Agilent 6890N)—mass spectrometer (Agilent 5975C) at 0, 4, 7, 10 and 12 incubation days. In addition, the optical density at 600 nm (OD₆₀₀) was measured during the culture period. Measurement of VOCs showed that chloromethane, bromomethane, iodomethane, isoprene, methanethiol, dimethyl sulfide, and dimethyl disulfide were produced in the culture of HKF-1. Dihalomethanes and trihalomethanes, such as dibromomethane, chloroiodomethane, bromoiodomethane, and tribromomethane, were not detected. Given that monohalomethanes and sulfur-containing VOCs were abundant in the culture, HKF-1 is one of the possible candidates as a producer of monohalomethane and sulfur-containing VOCs in marine environment, but not of di- or trihalomethanes.