Open AccessImprovement of the salt aggregation test to study bacterial cell‐surface hydrophobicity
Author(s) -
Rozgonyi Ferenc,
Szitha Katalin R.,
Ljungh Åsa,
Baloda Suraj B.,
Hjertén Stellan,
Wadström Torkel
Publication year - 1985
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1985.tb00999.x
Subject(s) - chemistry , methylene blue , chromatography , salt (chemistry) , ammonium , ammonium bicarbonate , bacterial cell structure , drop (telecommunication) , bacteria , biochemistry , organic chemistry , biology , raw material , telecommunications , photocatalysis , computer science , genetics , catalysis
An improved salt aggregation test (improved SAT) was developed to sensitize the determination of bacterial cell‐surface hydrophobicity. One drop of a fresh bacterial suspension standardized to an A 1cm 540 of 20 (equivalent to 5 × 10 9 cfu/ml), and one drop each of ammonium sulphate solutions stained with methylene blue, were mixed on a white hydrophobic paper card using toothpicks. The bacterial suspensions, methylene blue stock solutions and the ammonium sulphate solutions (0.01–4.0 M) were made in 0.02 M sodium phosphate buffer, pH 6.8. Bacterial aggregations were read immediately after mixing the salt/bacterial suspensions while the card was gently rocked. Readings were also confirmed the next day on dried preparations. The results proved independent of reading time and mixture conditions (wet or dry preparations). The improved SAT technique is very rapid and sensitive, the reaction is easily read with the naked eye, and the paper cards can be stored for documentation of aggregation patterns after drying. In the improved SAT, the Staphylococcus cells of different species aggregated in 5 ways: tiny, medial, flaky granular, particulated and macrofilamentous forms; Salmonella strains aggregated in flaky granular, particulated and macrofilamentous forms.