Characterization, Seasonal Occurrence, and Diel Fluctuation of Poly(hydroxyalkanoate) in Photosynthetic Microbial Mats

AUTOR(ES)

Rothermich, Mary M.

FONTE

American Society for Microbiology

RESUMO

In situ poly(hydroxyalkanoate) (PHA) levels and repeating-unit compositions were examined in stratified photosynthetic microbial mats from Great Sippewissett Salt Marsh, Mass., and Ebro Delta, Spain. Unlike what has been observed in pure cultures of phototrophic bacteria, the prevalence of hydroxyvalerate (HV) repeating units relative to hydroxybutyrate (HB) repeating units was striking. In the cyanobacteria-dominated green material of Sippewissett mats, the mole percent ratio of repeating units was generally 1HB:1HV. In the purple sulfur bacteria-dominated pink material the relationship was typically 1HB:2HV. In Sippewissett mats, PHA contributed about 0.5 to 1% of the organic carbon in the green layer and up to 6% in the pink layer. In Ebro Delta mats, PHA of approximately 1HB:2HV-repeating-unit distribution contributed about 2% of the organic carbon of the composite photosynthetic layers (the green and pink layers were not separated). Great Sippewissett Salt Marsh mats were utilized for more extensive investigation of seasonal, diel, and exogenous carbon effects. When the total PHA content was normalized to organic carbon, there was little seasonal variation in PHA levels. However, routine daily variation was evident at all sites and seasons. In every case, PHA levels increased during the night and decreased during the day. This phenomenon was conspicuous in the pink layer, where PHA levels doubled overnight. The daytime declines could be inhibited by artificial shading. Addition of exogenous acetate, lactate, and propionate induced two- to fivefold increases in the total PHA levels when applied in the daylight but had no effect when applied at night. The distinct diel pattern of in situ PHA accumulation at night appears to be related, in some phototrophs, to routine dark energy metabolism and is not influenced by the availability of organic nutrients.

Documentos Relacionados

• Characterization, occurrence, and molecular cloning of a 39-kilodalton Brucella abortus cytoplasmic protein immunodominant in cattle.
• Molecular characterization, occurrence, and immunogenicity in infected sheep and cattle of two minor outer membrane proteins of Brucella abortus.
• Observations on the Occurrence, Distribution, and Seasonal Incidence of Blue-green Algal Viruses
• Ammonia-oxidizing bacteria in a chloraminated distribution system: seasonal occurrence, distribution and disinfection resistance.
• Seasonal and Diel Variability in Dissolved DNA and in Microbial Biomass and Activity in a Subtropical Estuary