title: 111Indium labeling of microorganisms to facilitate the investigation of bacterial adhesion.
abstract: The ability of bacteria to adhere to polymeric interfaces has attracted considerable attention in recent years. Metabolic labeling of microorganisms with 35S-methionine or other beta-emitters is commonly utilized for quantification of bacterial adhesion to biopolymers. Since the use of these isotopes is cumbersome, the possibility of labeling the microorganisms with 111Indium, a strong gamma-emitter, was explored. This report demonstrates that bacteria can be easily labeled with 111Indium. Staphylococcus aureus, Staphylococcus epidermiids, and Pseudomonas aeruginosa were labeled with either 111Indium-oxine or 35S-methionine; and labeling efficiency, retention of incorporated labels, and growth kinetics of labeled bacteria were compared under identical experimental conditions. Bacteria labeled with 111In-oxine incorporated approximately 90% of radioactivity within 10 min, whereas 35S-methionine incorporation required many hours of incubation. Both the incorporated isotopes were gradually released by rapidly growing bacteria into the suspension medium. Of the total incorporated labels, approximately 20% 111In and 15% 35S were released in the surrounding medium every 24 h. No release of incorporated labels occurred when cells were fixed with 2.5% buffered glutaraldehyde. Growth kinetics and scanning or transmission electron microscopic analysis showed no detectable differences among control (nonlabeled), 111In-, or 35S-labeled bacteria. Labeling of bacteria with 111In-oxine does not interfere with bacterial adherence. These observations suggest that 111In incorporation provides a simple and rapid method of labeling of microorganisms. Compared to currently available techniques, the use of 111In-labeled bacteria will facilitate the quantitation of adherent bacteria to interfaces.
authors.affiliation: Artificial Heart Research Laboratory, University of Utah, Salt Lake City 84103.
authors.forename: R
authors.initials: R
authors.lastname: Ardehali
authors.forename: S F
authors.initials: SF
authors.lastname: Mohammad
mesh_terms: D001419:Bacteria / Q000254:growth & development; D001422:Bacterial Adhesion / Q000502:physiology*; D018407:Bacterial Physiological Phenomena; D002455:Cell Division; D007205:Indium Radioisotopes; D007553:Isotope Labeling; D008715:Methionine / Q000378:metabolism; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D015125:Oxyquinoline / Q000378:metabolism; D011108:Polymers; D013462:Sulfur Radioisotopes
chemical_list: D007205:Indium Radioisotopes; D011108:Polymers; D013462:Sulfur Radioisotopes; D015125:Oxyquinoline; D008715:Methionine