The Genus Geobacillus and Their Biotechnological Potential

Abstract

The genus Geobacillus comprises a group of Gram-positive thermophilic bacteria, including obligate aerobes, denitrifiers, and facultative anaerobes that can grow over a range of 45-75°C. Originally classified as group five Bacillus spp., strains of Bacillus stearothermophilus came to prominence as contaminants of canned food and soon became the organism of choice for comparative studies of metabolism and enzymology between mesophiles and thermophiles. More recently, their catabolic versatility, particularly in the degradation of hemicellulose and starch, and rapid growth rates have raised their profile as organisms with potential for second-generation (lignocellulosic) biorefineries for biofuel or chemical production. The continued development of genetic tools to facilitate both fundamental investigation and metabolic engineering is now helping to realize this potential, for both metabolite production and optimized catabolism. In addition, this catabolic versatility provides a range of useful thermostable enzymes for industrial application. A number of genome-sequencing projects have been completed or are underway allowing comparative studies. These reveal a significant amount of genome rearrangement within the genus, the presence of large genomic islands encompassing all the hemicellulose utilization genes and a genomic island incorporating a set of long chain alkane monooxygenase genes. With G+C contents of 45-55%, thermostability appears to derive in part from the ability to synthesize protamine and spermine, which can condense DNA and raise its Tm.

Experimental evolution of Bacillus subtilis

“…They have been isolated everywhere from the upper layers of the atmosphere to the depths of ocean trenches, and from almost every conceivable environment in between (Fajardo-Cavazos et al, 2014;Zeigler and Perkins, 2015). Members include not only mesophiles, but acidophiles (Ciuffreda et al, 2015), alikaliphiles (Preiss et al, 2015), halophiles (Hanelt and Muller, 2013), psychrophiles (Larkin and Stokes, 1966), thermophiles (Zeigler, 2014;Hussein et al, 2015) and UV-radiation tolerant organisms (Ordonez et al, 2009). Their physiological capabilities suggest they play a significant role in global carbon, nitrogen and sulphur cycles and in the degradation of plant, fungus and insect biomass (Mandic-Mulec and Prosser, 2011).…”

Draft Genome Sequence of Geobacillus sp. LEMMY01, a Thermophilic Bacterium Isolated from the Site of a Burning Grass Pile

“…can grow over a range of 45 to 75°C and seem to be ubiquitous (1). These characteristics make members of this genus highly suitable for biotechnological applications, as sources for thermostable enzymes with great potential for biocatalysis and production of potential novel secondary metabolites (2). …”

Development and implementation of rapid metabolic engineering tools for chemical and fuel production in Geobacillus thermoglucosidasius NCIMB 11955

“…Other microbial species are, however, being pursued, including thermophilic bacteria belonging to the genus Geobacillus. These aerobic or facultative anaerobic bacteria are able to ferment a wide range of sugars (glucose, cellobiose, xylose and mixtures of glucose, xylose, and arabinose), typical of those found in lignocellulosic substrates, and can grow over a wide range of temperatures between 40 and 70 °C [2]. Higher growth temperatures improve the rate of feed conversion and make the process more effective by reducing cooling costs during fermentation.…”