title: Comparison of cellulolytic activities in Clostridium thermocellum and Three thermophilic, cellulolytic anaerobes

authors: Reynolds, Paul H.S.

subjects: carboxymethyl cellulose

abstract: Avicelase, carboxymethyl cellulase (CMCase), and β-glucosidase activities have been compared between Clostridium thermocellum and three extremely thermophilic, cellulolytic anaerobes, isolates TP8, TP11, and KT8. The three isolates were all small, gram-negative staining, oval-ended rods which occurred singly and, at exponential phase, in long chains. They were nonflagellated and no spores were visible. The KT8 and TP11 isolates caused clumping of the cellulose during growth. In all four organisms the CMCase activity paralleled cell growth; however, in C. thermocellum and TP8 the avicelase activity did not increase until early stationary phase. Total CMCase activity in C. thermocellum was significantly higher than in the three isolates; however, avicelase activities were much more comparable among the four organisms. C. thermocellum produced higher levels of ethanol, and all four organisms produced similar concentrations of acetate. The amounts of free and bound CMCase and avicelase activities were investigated. In C. thermocellum and TP8 most of the CMCase and avicelase activities were bound to the cellulose in the medium. In contrast, most of the CMCase activity in TP1l and KT8 was free in the culture supernatant; a significant percentage of avicelase activity was also free. The TP8 isolate was also grown on a defined medium with urea as sole nitrogen source and cellulose serving as the carbon source. Under these conditions the pattern of enzyme production was the same as that in the enriched medium, although the level of that production was considerably reduced.

text: Comparison of cellulolytic activities in Clostridium thermocellum and Three thermophilic, cellulolytic anaerobes Avicelase, carboxymethyl cellulase (CMCase), and β-glucosidase activities have been compared between Clostridium thermocellum and three extremely thermophilic, cellulolytic anaerobes, isolates TP8, TP11, and KT8. The three isolates were all small, gram-negative staining, oval-ended rods which occurred singly and, at exponential phase, in long chains. They were nonflagellated and no spores were visible. The KT8 and TP11 isolates caused clumping of the cellulose during growth. In all four organisms the CMCase activity paralleled cell growth; however, in C. thermocellum and TP8 the avicelase activity did not increase until early stationary phase. Total CMCase activity in C. thermocellum was significantly higher than in the three isolates; however, avicelase activities were much more comparable among the four organisms. C. thermocellum produced higher levels of ethanol, and all four organisms produced similar concentrations of acetate. The amounts of free and bound CMCase and avicelase activities were investigated. In C. thermocellum and TP8 most of the CMCase and avicelase activities were bound to the cellulose in the medium. In contrast, most of the CMCase activity in TP1l and KT8 was free in the culture supernatant; a significant percentage of avicelase activity was also free. The TP8 isolate was also grown on a defined medium with urea as sole nitrogen source and cellulose serving as the carbon source. Under these conditions the pattern of enzyme production was the same as that in the enriched medium, although the level of that production was considerably reduced.

year: 1986

title: Holocene fluctuations of a meromictic Lake in southern British Columbia

authors: Lowe, David J.

abstract: Holocene deposits of Mahoney Lake, a meromictic saline lake located in a closed basin in the semi-arid Okanagan Valley, contain evidence of frequent and marked changes in lake depth (up to >12 m/100¹⁴C yr) probably caused by short-term changes in effective precipitation. We studied a 5.45-m-long core comprising a basal layer of inorganic mud overlain by a succession of layers of calcareous laminated and nonlaminated organic mud, marl, and sand. We used Mazama tephra to adjust nine radiocarbon ages for the hardwater effect. Meromixis developed ca. 9000¹⁴C yr B.P., and the lake has been episodically meromictic for about half the time since. Because of close linkages between sediments and depositional environments in meromictic and saline lakes, we infer that laminated sediments indicate meromictic conditions and high lake levels (>ca. 12 m water depth), whereas thick marl layers and nonlaminated sediments indicate nonmeromictic conditions and thus low lake levels (<ca. 8 m depth). Many of the inferred short-term climatic changes have not been identified in previous studies in northwestern North America, perhaps because of insensitive climatic proxies, inadequate temporal resolution, or discounting of anomalous findings.

text: Holocene fluctuations of a meromictic Lake in southern British Columbia Holocene deposits of Mahoney Lake, a meromictic saline lake located in a closed basin in the semi-arid Okanagan Valley, contain evidence of frequent and marked changes in lake depth (up to >12 m/100¹⁴C yr) probably caused by short-term changes in effective precipitation. We studied a 5.45-m-long core comprising a basal layer of inorganic mud overlain by a succession of layers of calcareous laminated and nonlaminated organic mud, marl, and sand. We used Mazama tephra to adjust nine radiocarbon ages for the hardwater effect. Meromixis developed ca. 9000¹⁴C yr B.P., and the lake has been episodically meromictic for about half the time since. Because of close linkages between sediments and depositional environments in meromictic and saline lakes, we infer that laminated sediments indicate meromictic conditions and high lake levels (>ca. 12 m water depth), whereas thick marl layers and nonlaminated sediments indicate nonmeromictic conditions and thus low lake levels (<ca. 8 m depth). Many of the inferred short-term climatic changes have not been identified in previous studies in northwestern North America, perhaps because of insensitive climatic proxies, inadequate temporal resolution, or discounting of anomalous findings.

year: 1997

title: The relationship between on-water performance and physical characteristics in elite and sub-elite outrigger canoe paddlers

authors: King, Tupuria

abstract: Objectives: The aim of the present study was to compare and investigate the relationship between 500 m on-water performance and physical characteristics in elite and sub-elite outrigger canoe paddlers. Methods: A total of 16 males participated in the study including eight elite paddlers (age: 24.8 ± 10.5 yrs., total paddling experience: 12.5 ± 5.2 yrs.) and eight sub-elite paddlers (age: 34.4 ± 15.4 yrs., total paddling experience: 6.8 ± 5.2 yrs.). Body mass, height, sitting height, arm span, arm length, body fat percentage, 50 kg muscular endurance (bench press and bench pull), peak oxygen uptake (VO2peak) and Wingate performance (30 sec maximal effort) were assessed and subsequently correlated with 500 m outrigger canoeing performance at a national championship’s regatta. Results: When group data were combined, moderate to strong correlations were found between 500 m outrigger canoeing performance and absolute VO2peak (r = -0.61), upper limb length (r = -0.60) 50 kg bench press (r = -0.56), total paddling experience (r = -0.53), body mass (r = -0.51), sitting height (r = -0.51), singles paddling experience (r = -0.49), height (r = -0.48) and Wingate distance (r = -0.42). When groups were compared, elite paddlers showed significantly greater Wingate mean power and distance, paddling experience and 500 m on-water performance times than sub-elite paddlers (p < 0.05). However, there were no significant differences in anthropometrical measures, muscular endurance and VO2peak between the two groups (p < 0.05). Conclusion: VO2peak and upper limb length were the best predictors of performance over the 500 m sprint distance across the entire group. Thirty-second Wingate mean power and distance, years of paddling experience and subsequent 500 m on-water performance differentiated elite from sub-elite paddlers.

text: The relationship between on-water performance and physical characteristics in elite and sub-elite outrigger canoe paddlers Objectives: The aim of the present study was to compare and investigate the relationship between 500 m on-water performance and physical characteristics in elite and sub-elite outrigger canoe paddlers. Methods: A total of 16 males participated in the study including eight elite paddlers (age: 24.8 ± 10.5 yrs., total paddling experience: 12.5 ± 5.2 yrs.) and eight sub-elite paddlers (age: 34.4 ± 15.4 yrs., total paddling experience: 6.8 ± 5.2 yrs.). Body mass, height, sitting height, arm span, arm length, body fat percentage, 50 kg muscular endurance (bench press and bench pull), peak oxygen uptake (VO2peak) and Wingate performance (30 sec maximal effort) were assessed and subsequently correlated with 500 m outrigger canoeing performance at a national championship’s regatta. Results: When group data were combined, moderate to strong correlations were found between 500 m outrigger canoeing performance and absolute VO2peak (r = -0.61), upper limb length (r = -0.60) 50 kg bench press (r = -0.56), total paddling experience (r = -0.53), body mass (r = -0.51), sitting height (r = -0.51), singles paddling experience (r = -0.49), height (r = -0.48) and Wingate distance (r = -0.42). When groups were compared, elite paddlers showed significantly greater Wingate mean power and distance, paddling experience and 500 m on-water performance times than sub-elite paddlers (p < 0.05). However, there were no significant differences in anthropometrical measures, muscular endurance and VO2peak between the two groups (p < 0.05). Conclusion: VO2peak and upper limb length were the best predictors of performance over the 500 m sprint distance across the entire group. Thirty-second Wingate mean power and distance, years of paddling experience and subsequent 500 m on-water performance differentiated elite from sub-elite paddlers.

year: 2019