PERSISTENCE OF A SURROGATE FOR A GENETICALLY-ENGINEERED CELLULOLYTIC MICROORGANISM AND EFFECTS ON AQUATIC COMMUNITY AND ECOSYSTEM PROPERTIES - MESOCOSM AND STREAM COMPARISONS
Tl. Bott et La. Kaplan, PERSISTENCE OF A SURROGATE FOR A GENETICALLY-ENGINEERED CELLULOLYTIC MICROORGANISM AND EFFECTS ON AQUATIC COMMUNITY AND ECOSYSTEM PROPERTIES - MESOCOSM AND STREAM COMPARISONS, Canadian journal of microbiology, 39(7), 1993, pp. 686-700
Our research objectives were to (i) determine the persistence of an in
troduced surrogate (Cellulomonas sp. NRC 2406) for a genetically engin
eered microorganism in sediments, growths of Cladophora glomerata (Chl
orophyta), and leaf packs, (ii) test community and ecosystem structura
l and functional responses to the introduced bacteria, and (iii) evalu
ate the utility of flowing water mesocosms as tools for assessing the
fates and effects of introduced bacteria in streams. Cellulomonas sp.
densities were determined using fluorescent antibodies; maxima were le
ss-than-or-equal-to 1% of the total bacterial community in each habita
t in two experiments, and almost-equal-to 25% of total densities in le
af packs in a third experiment. Densities declined from postinoculatio
n maxima faster in sediments than in C. glomerata growths and leaf pac
ks. Cellulomonas sp. persisted in leaf packs at densities significantl
y greater than background. Cellulomonas sp. had no statistically signi
ficant effects on primary productivity, community respiration, assimil
ation ratios, photosynthesis/respiration (P/R) ratios, bacterial produ
ctivity, and leaf litter decomposition rates. Cellulase concentrations
were positively correlated with Cellulomonas sp. densities greater-th
an-or-equal-to 7 x 10(8) cells/g dry mass in fresh leaf litter for 2 d
ays following exposure. Total bacterial densities, algal biomass, and
total viable biomass sometimes differed between control and experiment
al systems, but differences were not related to Cellulomonas sp. intro
duction. Mesocosms were good tools for studying bacterial population d
ynamics in leaf litter and physiological aspects of litter degradation
, but they were less well suited to measuring losses of litter mass an
d cellulose because physical abrasion during storms accelerated those
processes in the field.