TY - JOUR

T1 - The feasibility of using GFP-expressing Escherichia coli, coupled with fluorimetry, to determine protozoan ingestion rates.

AU - Parry, Jackie D.

AU - Heaton, Karen

AU - Drinkall, Janice

AU - Jones, Harriet L. J.

PY - 2001/3

Y1 - 2001/3

N2 - The feasibility of using a live Escherichia coli population, which had been engineered to express the green fluorescent protein (GFP), coupled with fluorimetry, was tested as a means for determining protozoan ingestion rates. Its potential use was based on evidence that once cells are acidified, e.g. in a food vacuole, the fluorescence is lost. Of the 29 protozoa tested, over 85% ingested the GFP-expressing E. coli and a detailed experiment with the ciliate Tetrahymena pyriformis was carried out, principally to assess the performance of the live bacterium against two commonly used surrogate prey, i.e. fluorescently labelled bacteria (FLB) and fluorescently labelled microspheres (FLMs). A decrease in GFP-expressing E. coli fluorescence and, hence, concentration, was recorded by fluorimetry and epifluorescence microscopy, with calculated ingestion rates being equivalent. A higher ingestion rate was determined by counting the number of fluorescent E. coli within the ciliate over 120 s, but this was equivalent to that obtained for the stained E. coli using the same direct method of analysis. However, the ciliate was shown to process the stained and unstained E. coli cells differently, with only the latter resulting in an increase in ciliate abundance.

AB - The feasibility of using a live Escherichia coli population, which had been engineered to express the green fluorescent protein (GFP), coupled with fluorimetry, was tested as a means for determining protozoan ingestion rates. Its potential use was based on evidence that once cells are acidified, e.g. in a food vacuole, the fluorescence is lost. Of the 29 protozoa tested, over 85% ingested the GFP-expressing E. coli and a detailed experiment with the ciliate Tetrahymena pyriformis was carried out, principally to assess the performance of the live bacterium against two commonly used surrogate prey, i.e. fluorescently labelled bacteria (FLB) and fluorescently labelled microspheres (FLMs). A decrease in GFP-expressing E. coli fluorescence and, hence, concentration, was recorded by fluorimetry and epifluorescence microscopy, with calculated ingestion rates being equivalent. A higher ingestion rate was determined by counting the number of fluorescent E. coli within the ciliate over 120 s, but this was equivalent to that obtained for the stained E. coli using the same direct method of analysis. However, the ciliate was shown to process the stained and unstained E. coli cells differently, with only the latter resulting in an increase in ciliate abundance.

KW - Protozoan ingestion

KW - GFP-expressing Escherichia coli

KW - Fluorescently labelled microsphere

KW - Fluorescently labelled bacteria

KW - Fluorimetry

U2 - 10.1016/S0168-6496(00)00106-9

DO - 10.1016/S0168-6496(00)00106-9

M3 - Journal article

VL - 35

SP - 11

EP - 17

JO - FEMS Microbiology Ecology

JF - FEMS Microbiology Ecology

SN - 0168-6496

IS - 1

ER -