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Pectinolytic enzymes of oral spirochetes from humans
Abstract:
Five strains of obligately anaerobic, pectin-fermenting spirochetes were isolated from the subgingival plaque of humans. The strains produced two extracellular enzymatic activities that functioned in pectin degradation. One of these enzymatic activities was pectin methylesterase (EC 3.1.1.11), and the other was pectate lyase (EC 4.2.2.2) of the endo type. The data indicate that the cumulative action of these two enzymatic activities brought about depolymerization of pectin in spirochete cultures. Pectin- or polygalacturonate-degrading hydrolases were not detected. A cell-associated lyase activity that catalyzed polygalacturonate breakdown was present in one of the spirochete strains. In addition to pectin, the isolates utilized polygalacturonic, glucuronic, or galacturonic acid as fermentable substrate but did not neutral sugars, amino acids, or other substrates tested. Although the oral spirochetes did not ferment hyaluronic acid, one of the strains grew in coculture with a hyaluronidase-producing Peptostreptococcus strain in a medium containing hyaluronic acid as fermentable substrate. Two of the isolates were identified as Treponema pectinovorum strains on the basis of their substrate utilization pattern, end products of fermentation, other phenotypic characteristics, and the guanine-plus-cytosine content of their DNA. Even though the pectinolytic isolates were specialized with respect to the fermentable substrates they utilized, they appeared to compete successfully with other microorganisms in their habitat.
Insights
Oral spirochetes isolated from human plaque ferment pectin using pectin methylesterase and pectate lyase enzymes. Two strains were identified as Treponema pectinovorum, demonstrating specialized substrate utilization.
Area of Science:
- Microbiology
- Enzymology
- Oral Biology
Background:
- Subgingival plaque harbors diverse microorganisms, including spirochetes.
- Pectin degradation is crucial in certain ecological niches.
- The metabolic capabilities of oral spirochetes are not fully understood.
Purpose of the Study:
- To isolate and characterize pectin-degrading spirochetes from human subgingival plaque.
- To identify the enzymes involved in pectin breakdown by these isolates.
- To determine the substrate utilization patterns and taxonomic identity of these spirochetes.
Main Methods:
- Isolation of obligately anaerobic spirochetes from human subgingival plaque.
- Enzyme assays for pectin methylesterase and pectate lyase activity.
- Substrate utilization tests including pectin, polygalacturonic acid, glucuronic acid, galacturonic acid, and hyaluronic acid.
- Phenotypic characterization and DNA guanine-plus-cytosine content analysis for taxonomic identification.
Main Results:
- Five strains of pectin-fermenting spirochetes were isolated.
- Extracellular pectin methylesterase (EC 3.1.1.11) and endo-type pectate lyase (EC 4.2.2.2) activities were identified.
- Pectin depolymerization was attributed to the combined action of these enzymes.
- Isolates utilized pectin, polygalacturonic acid, glucuronic acid, and galacturonic acid, but not neutral sugars or amino acids.
- Two strains were identified as Treponema pectinovorum based on multiple characteristics.
Conclusions:
- Oral spirochetes possess specialized enzymatic machinery for pectin degradation.
- Treponema pectinovorum strains contribute to pectin breakdown in the subgingival environment.
- These specialized pectinolytic isolates compete effectively within their oral habitat.