A. Navarrete et al., Physiological status and community composition of microbial mats of the Ebro Delta, Spain, by signature lipid biomarkers, MICROB ECOL, 39(1), 2000, pp. 92-99
Physiological status of microbial mats of the Ebro Delta (Tarragona, Spain)
based on the extraction of lipids considered "signature lipid biomarkers"
(SLB) from the cell membranes and walls of microorganisms has been analyzed
. Data from a day-night cycle show significant differences in viable cells
countings (PLFA cells counts) ranging from 1.5 x 10(10) to 5.0 x 10(10) cel
ls g(-1) of sediment. Minimum values were observed at 18:00 and 6:00, when
physicochemical conditions change drastically. The diversity of the microbi
al community was assessed by GC/MS analysis of phospholipid fatty acids (PL
FA). The ratio of PLFA, representative of Gram-negative bacteria, comprises
47.8% of the total PLFA of the microbial mat community. The remaining PLFA
was representative of Gram-positive (10.0%), anaerobic (5.7%), and eukaryo
tic microorganisms (5.7%), and other common lipids. Two different approache
s were used as a comparative study to assess the physiological status of th
e microbial mats. Two parameters (cyclopropane fatty acids/omega 7c monoeno
ic fatty acids, and measurement of the trans/cis monoenoic PLFA ratio) show
ed a minimum at midnight, suggesting the highest microbial activity. Higher
values were observed at 18:00 and 6:00, coinciding with lower PLFA cell co
unts.