Diversity and Activity of Aquatic Cellulolytic Bacteria Isolated from Sedimentary Water in the Littoral Zone of Tonle Sap Lake, Cambodia

Abstract

Tonle Sap Lake is the largest freshwater lake in Southeast Asia, and it is regarded as one of the most biodiverse freshwater ecosystems in the world. Studies concerning aquatic cellulolytic bacteria from Tonle Sap Lake remain scarce. Cellulolytic bacteria and their cellulases play a vital role in the biogeochemical cycles of lake environments, and their application in biotechnological industries is likewise an important component of their usage. This study aimed to assess the isolation, genetic identification, bioinformatic analyses, and activity characterization of aquatic cellulolytic bacteria. The cellulolytic bacteria isolated from sedimentary water samples in the littoral zone of the lake belong to the genera Aeromonas, Bacillus, and Exiguobacterium. Several isolated aquatic bacteria were designated as rare cellulolytic microbes. Remarkably, B. mojavensis strain REP303 was initially evidenced by the aquatic cellulolytic bacterium in freshwater lake ecosystems. It was considered a highly active cellulolytic bacterium capable of creating a complete cellulase system involving endoglucanase, exoglucanase, and β-glucosidase. The encoded endoglucanase belongs to the glycosyl hydrolase family 5 (GH5), with a carboxymethylcellulase (CMCase) activity of 3.97 ± 0.05 U/mL. The optimum temperature and pH for CMCase activity were determined to be 50 °C at a pH of 7.0, with a stability range of 25–55 °C at a neutral pH of 7.0–8.0. The CMCase activity was enhanced significantly by Mn2+ and was inhibited considerably by EDTA and ethyl-acetate. In conclusion, this study is the first to report data concerning aquatic cellulolytic bacteria isolated from the littoral zone of Tonle Sap Lake. A novel strain of isolated cellulolytic B. mojavensis could be applied in various cellulose-based industries.

Diversity and activity of amylase-producing bacteria isolated from mangrove soil in Thailand

“…Furthermore, Luang-In et al (2019) had studied the isolation of amylase-producing bacteria from soil and also found this conflict in their results. This conflicting result could be due to the fluctuations in some experimental factors, which affected the production of bacterial extracellular enzyme (Chantarasiri 2021c).…”

“…All spotted plates were incubated at a temperature of 30.01°C for 24 h in a KB720 incubator and then flood-plated with an iodine solution for 10 min. The iodine solution contained 0.33 g of I2 (Ajax Finechem, Australia) and 0.67 g of KI (Ajax Finechem, Australia) in 100 mL of distilled water (Chantarasiri 2021c). The amylase-producing isolates were detected by the amylolytic zone around their colonies on the starch agar after being stained with iodine solution.…”

Evaluation of the Influence of Habitat Heterogeneity and Human Activities on the Distribution of Microbial Diversity in a High Elevation Drop River

“…The functions of an ecosystem are based on its microbial diversity and structure [2]. Bacteria are the most important components of aquatic ecosystems, playing an important role in energy conversion, material circulation, and element accumulation and migration [3]. For example, bacteria are essential in the carbon cycle of rivers, where they treat organic carbon in flowing water bodies [4].…”

“…The results of this study can provide guidance for understanding the interaction between human beings and the environment, ecological environment maintenance, and biodiversity protection in the Huotong River. The main objectives of the study were: (1) to analyze the species composition and diversity of bacterial flora in water and sludge of the Huotong River; (2) to evaluate the effects of human disturbance on the species composition, diversity, and community structure of bacterial flora; (3) to analyze the spatial distribution characteristics of pathogenic bacteria and their potential effects on human health; and (4) to provide a scientific basis for the maintenance of the Huotong River ecosystem health and biodiversity protection.…”