title: Trace amounts of furan-2-carboxylic acids determine the quality of solid agar plates for bacterial culture.
abstract: BACKGROUND
  Many investigators have recognised that a significant proportion of environmental bacteria exist in a viable but non-culturable state on agar plates, and some researchers have also noticed that some of such bacteria clearly recover their growth on matrices other than agar. However, the reason why agar is unsuitable for the growth of some bacteria has not been addressed.
  
  
  RESULTS
  According to the guide of a bioassay for swarming inhibition, we identified 5-hydroxymethylfuran-2-carboxylic acid (5-HMFA) and furan-2-carboxylic acid (FA) as factors that inhibit bacterial swarming and likely inhibit extracellular polysaccharide production on agar. The furan-2-carboxylic acids 5-HMFA and FA effectively inhibited the swarming and swimming of several environmental bacteria at concentrations of 1.8 and 2.3 µg L(-1) (13 and 21 nmol L(-1)), respectively, which are equivalent to the concentrations of these compounds in 0.3% agar. On Luria-Bertani (LB) plates containing 1.0% agar that had been previously washed with MeOH, a mixture of 5-HMFA and FA in amounts equivalent to their original concentrations in the unwashed agar repressed the swarming of Escherichia coli K12 strain W3110, a representative swarming bacterium.
  
  
  CONCLUSIONS
  Agar that contains trace amounts of 5-HMFA and FA inhibits the proliferation of some slow-growing or difficult-to-culture bacteria on the plates, but it is useful for single colony isolation due to the ease of identification of swarmable bacteria as the non-swarmed colonies.
authors: Graduate School of Agriculture and Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
authors: Shintaro
authors: S
authors: Hara
authors: Reika
authors: R
authors: Isoda
authors: Teemu
authors: T
authors: Tahvanainen
authors: Yasuyuki
authors: Y
authors: Hashidoko
mesh_terms: D000362:Agar / Q000737:chemistry*; D049109:Cell Proliferation; D003470:Culture Media / Q000737:chemistry*; D048168:Escherichia coli K12 / Q000254:growth & development*; D005663:Furans / Q000737:chemistry*; D011786:Quality Control
chemical_list: D003470:Culture Media; D005663:Furans; D000362:Agar; C060089:2-furoic acid