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Carbon : nitrogen : phosphorus ratios influence biofilm formation by Enterobacter cloacae and Citrobacter freundii
Author(s) -
Thompson L.J.,
Gray V.,
Lindsay D.,
Von Holy A.
Publication year - 2006
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2006.03003.x
Subject(s) - citrobacter freundii , enterobacter cloacae , phosphorus , citrobacter , biofilm , enterobacter , microbiology and biotechnology , nitrogen , chemistry , carbon fibers , enterobacteriaceae , biology , bacteria , biochemistry , organic chemistry , escherichia coli , materials science , genetics , gene , composite number , composite material
Aims: To test the effects of C : N : P ratio modification of a well‐known nutrient medium formulation, the Endo formulation on biofilm formation by Enterobacter cloacae Ecl and Citrobacter freundii Cf1 in both single‐species and binary species biofilms. Methods and Results: The C : N : P atom : atom ratio of a well‐known nutrient medium formulation, the Endo formulation, that has been applied in fermentative biohydrogen studies, was modified to include two different C concentrations, one containing 17·65 g l −1 and the other 8·84 g l −1 sucrose, each containing four different C : N : P ratios, two at higher C : N : P ratios (334 : 84 : 16·8 and 334 : 84 : 3) and two at lower C : N : P ratios (334 : 28 : 5·6 and 334 : 28 : 1). Attached cells were enumerated after dislodging the biofilms that had formed on granular activated carbon (GAC). The modified medium containing 17·65 g l −1 sucrose and having a C : N : P ratio of 334 : 28 : 5·6 resulted in significantly ( P < 0·05) higher counts of attached cells for both single‐species biofilms at 7·73 log 10 CFU g −1 GAC and 9·3 log 10 CFU g −1 GAC for Ent. cloacae Ecl and Cit. freundii Cf1, respectively, and binary species biofilms at 8·2 log 10 CFU g −1 GAC and 6·34 log 10 CFU g −1 GAC for Ent. cloacae Ecl and Cit. freundii Cf1, respectively. Scanning electron micrographs showed qualitative evidence that the 334 : 28 : 5·6 ratio encouraged more complex and extensive biofilm growth for both single‐species and binary species biofilms. Conclusions: The differences in the attachment numbers between the different ratios were found not to be a result of the individual actions of the bacterial isolates involved but rather because of the effects of the various C : N : P ratios. The 334 : 28 : 5·6 ratio showed significantly ( P < 0·05) higher counts of attached cells for both single‐species and binary species biofilms. Significance and Impact of the Study: This study indicates that C : N : P ratios should be a key consideration with regard to maximizing biofilm formation in shake flask and fluidized bed bioreactor studies as well as understanding fundamental factors affecting biofilm growth in natural environments.