2.1. Isolation and identification of bacterial contaminants
Samples collected from a Midwestern dry-grind fuel ethanol
plant were serially diluted in phosphate buffered saline and spread
on plates containing MRS medium (Difco Becton Dickinson, Sparks,
MD) with 0.001% (w/v) cycloheximide added to suppress yeast
growth (Skinner and Leathers, 2004). Cultures were incubated
anaerobically at 37 C using the Mitsubishi AnaeroPack system
(Thermo Fisher Scientific, Pittsburg PA) or the GasPak EZ System
(Becton Dickinson) and strains were purified twice as single colonies
and stored at 80 C in 40% (v/v) glycerol in 96-well microtiter
plates.
Strains were identified by sequencing of 16S rRNA genes via
polymerase chain reaction using 16Sf (50
-GAGAGTTTGATYCTGGC
TCAG) and 16Sr (50
-GAAGGAGGTGWTCCARCCGCA) primers as previously
described (Whitehead and Cotta, 2001). The resulting products
(about 1.6 kbp) were purified using a 5 Prime PCR purification
kit, and sequenced by standard methods using the forward primer.
The sequences obtained were compared with sequences in the
GenBank database using BLASTN program (Altschul et al., 1997)
at the National Center for Biotechnology Information (http://
blast.ncbi.nlm.nih.gov/).
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