Lactococcus lactis subsp. cremoris Ropy 352 and L. lactis
subsp. cremoris Hollandicus produce an exopolysaccharide (EPS) that
imparts commercially desirable textural and rheological properties
to fermented milk products. This ropy phenotype is expressed under
specific environmental conditions. A mucoid EPS phenotype, also
expressed under specific environmental conditions, but not involved
in the fermentation of ropy milk was identified. The two EPS
phenotypes can be expressed individually or concurrently.
Genetic regulators involved in expression of the EPS
phenotypes were sought. DNA probes and polyclonal antiserum
specific to two regulators of EPS in Escherichia coli, Lon protease
and RcsA protein, were used to probe ropy and non-ropy strains of L.
lactis. The two ropy strains of L. lactis subsp. cremoris, Ropy 352
and Hollandicus, expressed significantly less of the Lon protein than
non-ropy strains.
Southern and Western blot analysis was extended to a number
of Gram negative and Gram positive bacteria. All of the Gram
negative bacteria probed contained DNA sequences that hybridized to
the Ion and rcsA gene probes, and all of these bacteria has at least
one protein that reacted with antiserum to E. coli Lon and RcsA
proteins. Two of the Gram positive bacteria contained DNA
sequences that hybridized to the E. coli rcsA probe. None of the
other Gram positive organisms contained DNA sequences that
hybridized to the rcsA or the Ion probes. However, all the Gram
positive bacteria contained one high molecular weight protein that reacted with Lon antiserum. In addition, Streptococcus salivarius expressed a protein that reacted with RcsA antiserum.
In the course of this study, a second RcsA protein was identified in E. coll. The two RcsA proteins are expressed from one rcsA gene. One RcsA protein is not the proteolytic product of the other RcsA protein. Limited peptide digest profiles of each RcsA protein reveals almost identical peptides indicating the two proteins share a high degree of homology but are not identical.
Ferguson plot analysis strongly suggests that the two RcsA proteins differ by size not by charge. Neither RcsA protein can be detected in cells mutant for Ion and rcsB. / Graduation date: 1997
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34322 |
| Date | 12 June 1996 |
| Creators | Dierksen, Karen P. |
| Contributors | Trempy, Janine E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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