Isolation and Characterization of Acidothermus cellulolyticus gen. nov., sp. nov., a New Genus of Thermophilic, Acidophilic, Cellulolytic Bacteria

Abstract

Twelve isolates of thermophilic, acidophilic, cellulolytic bacteria were obtained from three different primary enrichment cultures from acidic hot springs at Yellowstone National Park, Wyo. The three isolates which had the highest cellulolytic activity, as shown by the diameter of clearing zones surrounding colonies on cellulose agar plates, were selected for intensive study. All were gram-variable, nonsporulating aerobic rods which formed no pigment. They grew at 37 to 65"C, with optimum growth at 55°C. The pH range for growth was 3.5 to 7, with an optimum pH of 5. The guanine-plus-cytosine content of the deoxyribonucleic acid was 60.7 k 0.6 mol%. The organisms are resistant to penicillin G at 100 pglml. They share several important features with Thermus strains, namely heterotrophic, aerobic, and thermophilic mode of growth; morphological features; sensitivity to lysozyme; and presence of catalase. They differ in other important aspects, such as the pattern of carbon sources utilized for growth, the pH and temperature profiles of growth, the pattern of sensitivity to antibiotics, the guanine-plus-cytosine content of DNA, the composition of amino acids in the cell walls, and the structure of the cell walls. Thermus species are very sensitive to penicillin G, whereas our strains are resistant. Our strains also are different, in important respects, from the genus Thermomicrobium. Therefore, we designate the organism Acidothermus ceZZuZoZyticus gen. nov., sp. nov., of which the type strain is our strain 11B, ATCC 43068.This research effort was undertaken as part of a research program on the production of fuel alcohol from cellulosic biomass materials. The driving hypothesis is that a thermophilic, acidophilic, cellulolytic bacterium can be grown in coculture with other thermotolerant microorganisms to produce ethanol at a high rate from cellulosic wastes. Alternatively, the cellulolytic organism could be used to produce cellulase, which could be added to a cellulose-containing culture of an organism which ferments glucose to ethanol.Most of the thermophilic, cellulolytic microorganisms isolated to date are sporeforming anaerobes belonging to the genus Clostridium. None of these are acidophilic, and all have an optimum pH near 7. Thus, they would not grow well under the acidic conditions (pH 3 to 5 ) prevalent in an ethanolic fermentation.Aerobic, thermophilic, cellulolytic microorganisms include several species of fungi (10) and a few species of filamentous bacteria belonging to the family Actinomycetaceae (33). Among the fungi, Myceliophthora thermophila is of considerable interest, since it grows well on cellulose in submerged culture at 50°C and pH 4.5 and synthesizes cellulolytic enzymes (10). Thus, the organism is acidophilic, as well as cellulolytic and thermophilic. Rosenberg (24) screened 21 species of thermophilic and thermotolerant fungi for the ability to degrade cellulose and found that 13 species had this ability. It was not determined whether these organisms could grow well in submerged culture under...

Proposal for a New Hierarchic Classification System, Actinobacteria classis nov.

“…masc. n. Acidothermus, type genus of the family; -aceae, (102). A phylogenetic analysis has been published previously (123).…”

Culture-Independent Phylogenetic Analysis of the Microbial Community in Industrial Sugarcane Bagasse Feedstock Piles

“…28) Lignocellulolytic bacteria of the classes Bacilli and Actinobacteria have been reported in soils and waste sites with high lignocellulose content, 29,30) and their synergism in the degradation of sugarcane cellulose has been reported. 31) In this study, several potential lignocellulose-degrading aerobic bacteria including ones from genera Alicyclobacillus, Paenibacillus, and Thermomonospora and a lignocellulolytic species, Acidiothermus cellulolyticus capable of producing a variety of extracellular and cellulosomal-lignocellulose degrading enzyme systems, [32][33][34][35] could play a concerted role in bagasse decomposition. In addition, Bacteroidetes and Acidobacteria could also contribute significantly to lignocellulose degradation in the ecosystem.…”

Xyn10A, a Thermostable Endoxylanase from Acidothermus cellulolyticus 11B

“…With the current dependence on acid and heat pretreatment of lignocellulosic feedstocks, bioconversion enzymes from thermoacidophilic microbes are of particular value (25). Here we report the characterization of a thermostable glycoside hydrolase family 10 (GH10) xylanase (designated Xyn10A) from Acidothermus cellulolyticus 11B, a Gram-positive actinomycete that was isolated from acidic hot springs in Yellowstone National Park (4,18).…”