Grazing rates of diverse morphotypes of bacterivorous ciliates feeding on four allochthonous bacteria.
OBJECTIVE
The permanence in aquatic systems of allochthonous bacteria coming from sewage effluents is a risk for public health. This work aimed to analyse the elimination of the bacteria Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli and Klebsiella pneumoniae by a riverine ciliate community.


RESULTS
The ciliates were characterized and identified on the basis of morphological and behavioural features and grouped in nine morphotypes. Differential grazing by each morphotype on the four allochthonous bacteria was carried out by adding fluorescently labelled bacteria to the water samples, and measuring their uptake along time.


CONCLUSIONS
The nine morphotypes were present in all the samples but in different proportions, being the most abundant the small scuticociliates and hipotrichs. The smallest morphotypes showed grazing rates lower than 20 FLB ciliate(-1) h(-1), with a preference towards K. pneumoniae. The larger morphotypes showed in general the highest grazing rates, but the selectivity was hardly attributable to bacterial size or type of cell wall.


CONCLUSIONS
The elimination of allochthonous bacteria in an aquatic system may be highly different depending on the diversity of the ciliated protistan community in the system and on the nature of the bacterial prey.
Ayo
B
B
Departamento de Inmunología, Microbiología y Parasitología, Facultad de Ciencias, Universidad del Pais Vasco, Apartado 644, E-48080 Bilbao, Spain.
Santamaría
E
E
Latatu
A
A
Artolozaga
I
I
Azúa
I
I
Iriberri
J
J
D000818:Animals; D001419:Bacteria; D016798:Ciliophora / Q000145:classification / Q000502:physiology* / Q000648:ultrastructure; D015169:Colony Count, Microbial; D013293:Enterococcus faecalis / Q000502:physiology; D004926:Escherichia coli / Q000502:physiology; D005456:Fluorescent Dyes; D007711:Klebsiella pneumoniae / Q000502:physiology; D010587:Phagocytosis; D012722:Sewage / Q000382:microbiology*; D013212:Staphylococcus epidermidis / Q000502:physiology; D014871:Water Microbiology
D005456:Fluorescent Dyes; D012722:Sewage