Cellulolytic bacteria from soils in harsh environments

Abstract

It is believed that the exposure of organisms to harsh climate conditions may select for differential enzymatic activities, making the surviving organisms a very promising source for bioprospecting. Soil bacteria play an important role in degradation of organic matter, which is mostly due to their ability to decompose cellulose-based materials. This work focuses on the isolation and identification of cellulolytic bacteria from soil found in two environments with stressful climate conditions (Antarctica and the Brazilian semi-arid caatinga). Cellulolytic bacteria were selected using enrichments at high and low temperatures (4 or 60°C) in liquid media (trypic soy broth-TSB and minimum salt medium-MM) supplemented with cellulose (1%). Many of the isolates (119 out of 254-46.9%) displayed the ability to degrade carboxymethyl-cellulose, indicating the presence of endoglucolytic activity, while only a minority of these isolates (23 out of 254-9.1%) showed exoglucolytic activity (degradation of avicel). The obtained isolates revealed a preferential endoglucolytic activity according to the temperature of enrichments. Also, the identification of some isolates by partial sequencing of the 16S rRNA gene indicated that the Bacteroidetes (e.g., Pedobacter, Chryseobacterium and Flavobacterium) were the main phylum of cellulolytic bacteria isolated from soil in Antarctica; the Firmicutes (e.g., Bacillus) were more commonly isolated from samples from the caatinga; and Actinobacteria were found in both types of soil (e.g., Microbacterium and Arthrobacter). In conclusion, this work reports the isolation of bacteria able to degrade cellulose-based material from soil at very low or very high temperatures, a finding that should be further explored in the search for cellulolytic enzymes to be used in the bioenergy industry.

Characterization of heavy metals resistant heterotrophic bacteria from soils in the Windmill Islands region, Wilkes Land, East Antarctica

“…Our study revealed promising bacterial strains that could be a valuable source of industrially important cold active pro− teases, cellulases, xylanases, b−gucosidases, phytases. As the complete degrada− tion of cellulose requires the activity of diverse enzymes, isolation of cellulotic en− zymes active over a wide range of temperatures is highly desirable (Soares et al 2012). In this regard, cellulase and xylanase producing strains Vi−1, Vi−2, Vi−3, Vi−5 and Vi−7 would be of particular interest.…”

Optimization of Endoglucanase Production from a Novel Bacterial Isolate, Arthrobacter sp. HPG166 and Characterization of Its Properties

“…Athrobacter species are predominant members of culturable soil bacteria and can utilize a wide variety of organic compounds, such as aromatic hydrocarbons, nucleic acids and their degradation products, herbicides (Crocker et al 2000). However, there have been rare reports that strains of this species could be cellulolytic (Jones and Keddie 2006;Soares et al 2012). In this study, a potential novel cellulolytic bacterium Arthrobacter sp.…”

“…Therefore, Athrobacter species were thought to play a significant role in the biodegradation of organic matter (Cacciari and Lippi 1987;Crocker et al 2000;Jones and Keddie 2006;Niewerth et al 2012). However, Arthrobacter have been rarely reported as cellulose-degrading bacteria (Jones and Keddie 2006;Soares et al 2012). Furthermore, the close relatives of Arthrobacter sp.…”

Enzymatic activity of actinobacteria from semiarid

“…Essas condições são impostas em especial, pelas variações pluviométricas baixas, geralmente abaixo de 800 mm anuais e concentradas em apenas um período do ano, associadas com uma forte intensidade luminosa (Gorlach-Lira e Coutinho, 2007). Assim, solos sob vegetação de Caatinga são habitats bastante peculiares, com características próprias, cuja atividade biológica embora extremamente rica, ainda é pouco explorada (Soares Jr et al, 2012). Kavamura (2012) reportou a predominância de actinobactérias em relação a outros microorganismos do solo, como fungos, principalmente no período de menor pluviosidade.…”