Isolation of Pectin Degrading Thermophilic Bacteria

Pectin is a heterosaccharide found in the primary cell walls of many land plants. The breakdown of pectin is important in many industrial applications. Using thermophilic pectinases (pectindegrading enzymes) can confer many advantages in these applications, but only few of these enzymes are known. To work towards the goal of identifying novel thermophilic pectinases, pectin-degrading enrichments were established at 74 °C using material obtained from a hot spring in northern Nevada. Stable cultures were obtained under both anaerobic and microaerobic conditions, and attempts at isolation on solid medium successfully yielded pure cultures. The anaerobic isolate had a 16S rRNA gene sequence 99.8% identical to that of Thermotoga petrophila, which has been previously shown to degrade pectin. The microaerophilic sample yielded an isolate that contained an rRNA gene sequence that was 99.8% identical (1382/1385) to that of Thermus thermophilus JL-18, as species that is not known to degrade pectin. The capacity to use pectin as the sole carbon source was confirmed for both strains. Because the anaerobic isolate did not represent the dominant cellular morphotype in the enrichment cultures, isolation by the dilution to extinction method in liquid medium was also performed under anaerobic conditions. This resulted in isolation of a stain that may represent a new species in the genus Caldicellulosiruptor (98.9% rRNA gene identity). This strain is being further characterized in comparison to its closest relative, C. owensense, to determine if it represents a distinct species