Mf. Delosreyes et al., QUANTIFICATION OF GORDONA-AMARAE STRAINS IN FOAMING ACTIVATED-SLUDGE AND ANAEROBIC DIGESTER SYSTEMS WITH OLIGONUCLEOTIDE HYBRIDIZATION PROBES, Applied and environmental microbiology, 64(7), 1998, pp. 2503-2512
Previous studies have shown the predominance of mycolic acid-containin
g filamentous actinomycetes (mycolata) in foam layers in activated slu
dge systems, Gordona (formerly Nocardia) amarae often is considered th
e major representative of this group in activated sludge foam. In this
study, small-subunit rRNA genes of four G. amarae strains were sequen
ced, and the resulting sequences were compared to the sequence of G. a
marae type strain SE-6, Comparative sequence analysis showed that the
five strains used represent two lines of evolutionary descent; group 1
consists of strains NM23 and ASAC1, and group 2 contains strains SE-6
, SE-102, and ASF3. The following three oligonucleotide probes were de
signed: a species-specific probe for G. amarae, a probe specific for g
roup 1, and a probe targeting group 2, The probes were characterized b
y dissociation temperature and specificity studies, and the species-sp
ecific probe was evaluated for use in fluorescent in situ hybridizatio
ns. By using the group-specific probes, it was possible to place addit
ional G, amarae isolates in their respective groups, The probes were u
sed along with previously designed probes in membrane hybridizations t
o determine the abundance of G, amarae, group 1, group 2, bacterial, m
ycolata, and Gordona rRNAs in samples obtained from foaming activated
sludge systems in California, Illinois, and Wisconsin. The target grou
ps were present in significantly greater concentrations in activated s
ludge foam than in mixed liquor and persisted in anaerobic digesters.
Hybridization results indicated that the presence of certain G. amarae
strains may be regional or treatment plant specific and that previous
ly uncharacterized G, amarae strains may be present in some systems.