2.2. Microbial cultures
Although all of the cultures used in this study have been
successfully preserved in the ATCC repository for many
decades (e.g. Bacillus subtilis ATCC 6633 was added in
1938), the most recent production lots (yr. 2002–2005) that are
currently distributed to users were selected. Freeze-dried
bacterial cultures in serum or batch vials (B. subtilis ATCC
6633, and Clostridium sporogenes ATCC 11437) were
rehydrated at room temperature in TSB for 30 min and
transferred to TSA slants for working stocks. C. sporogenes
ATCC 11437 is a strict anaerobe and was rehydrated and grown
in reinforced clostridia broth (ATCC media no. 2107) under
anaerobic conditions before transferring to an anaerobic slant
culture. Anaerobic growth of C. sporogenes ATCC 11437 was
achieved using a commercial gas pack (GasPak™ EZ
Anaerobic Container System, Cat. No. 260678, Becton
Dickinson) for agar plates or in broth with 80% N2/20% CO2
head space gas. Freeze-dried fungal cultures were rehydrated in
sterile distilled water for at least 4 h. Aspergillus niger ATCC
16404 was grown on potato dextrose agar (PDA) slants, Candida
albicans ATCC 10231 and Sacchromyces cerevisiae
ATCC 9763 on yeast mold agar (YM agar) slants. All cultures
were passaged at least twice, but never more than five transfers,
on each medium (animal or vegetable-based) to limit nutrient
carry-over and allow stabilization of metabolic pathways prior
to any phenotypic testing.