Functional characterization of the galactan utilization system of <i><scp>G</scp>eobacillus stearothermophilus</i>

Tabachnikov, Orly; Shoham, Yuval

doi:10.1111/febs.12089

Cited by 54 publications

(51 citation statements)

References 52 publications

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“…lus shows no detectable activity toward lactose (31). In B. subtilis, the physiological role of GanA is to hydrolyze the transported short ␤-1,4-galacto-oligosaccharides into galactose, while it is unable to degrade the galactan polymer similar to GanB of G. stearothermophilus (31).…”

Section: Figmentioning

confidence: 99%

“…In B. subtilis, the physiological role of GanA is to hydrolyze the transported short ␤-1,4-galacto-oligosaccharides into galactose, while it is unable to degrade the galactan polymer similar to GanB of G. stearothermophilus (31). The arrangement of GH family 53-and GH family 42-encoding enzymes within the galactan utilization cluster was already reported for Geobacillus stearothermophilus (31). It seems a common feature that the degradation of galactan in nature is carried out by an extracellular endo-␤-galactanase that cleaves the high-molecular-weight polysaccharide inside the chain and produces short oligomers.…”

Section: Figmentioning

confidence: 99%

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Role of theganSPQABOperon in Degradation of Galactan by Bacillus subtilis

2016

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Bacillus subtilis possesses different enzymes for the utilization of plant cell wall polysaccharides. This includes a gene cluster containing galactan degradation genes (ganA and ganB), two transporter component genes (ganQ and ganP), and the sugarbinding lipoprotein-encoding gene ganS (previously known as cycB). These genes form an operon that is regulated by GanR. The degradation of galactan by B. subtilis begins with the activity of extracellular GanB. GanB is an endo-␤-1,4-galactanase and is a member of glycoside hydrolase (GH) family 53. This enzyme was active on high-molecular-weight arabinose-free galactan and mainly produced galactotetraose as well as galactotriose and galactobiose. These galacto-oligosaccharides may enter the cell via the GanQP transmembrane proteins of the galactan ABC transporter. The specificity of the galactan ABC transporter depends on the sugar-binding lipoprotein, GanS. Purified GanS was shown to bind galactotetraose and galactotriose using thermal shift assay. The energy for this transport is provided by MsmX, an ATP-binding protein. The transported galacto-oligosaccharides are further degraded by GanA. GanA is a ␤-galactosidase that belongs to GH family 42. The GanA enzyme was able to hydrolyze short-chain ␤-1,4-galacto-oligosaccharides as well as synthetic ␤-galactopyranosides into galactose. Thermal shift assay as well as electrophoretic mobility shift assay demonstrated that galactobiose is the inducer of the galactan operon regulated by GanR. DNase I footprinting revealed that the GanR protein binds to an operator overlapping the ؊35 box of the A -type promoter of P gan , which is located upstream of ganS. IMPORTANCEBacillus subtilis is a Gram-positive soil bacterium that utilizes different types of carbohydrates, such as pectin, as carbon sources. So far, most of the pectin degradation systems and enzymes have been thoroughly studied in B. subtilis. Nevertheless, the B. subtilis utilization system of galactan, which is found as the side chain of the rhamnogalacturonan type I complex in pectin, has remained partially studied. Here, we investigated the galactan utilization system consisting of the ganSPQAB operon and its regulator ganR. This study improves our knowledge of the carbohydrate degradation systems of B. subtilis, especially the pectin degradation systems. Moreover, the galactan-degrading enzymes may be exploited for the production of galacto-oligosaccharides, which are used as prebiotic substances in the food industry. S oil microorganisms are usually able to degrade a variety of polysaccharides and carbohydrates found in soil, including the remains of plants and especially the plant cell wall. The primary cell wall of plants is composed of different polysaccharide components, including cellulose, hemicellulose, and pectin, while the secondary cell walls are rigidified by lignin (1, 2). Among them, pectin is a family of galacturonic acid-rich polysaccharides that consists of the following three major pectic polysaccharide types: a linear component of poly...

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Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

Role of theganSPQABOperon in Degradation of Galactan by Bacillus subtilis

2016

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“…Nine of the ten completed genomes contain at least some portion of this island, and seven contain nearly all of it (see Table 1 for a summary and Table S3 for details). Recently, a galactan utilization operon has also been identified in strain T-6, enabling the bacterium to break down a key component of pectin, type I galactan (Tabachnikov & Shoham, 2013). The entire 9.4 kb cluster is also found in orthologous form in the genome of Geobacillus thermoleovorans CCB_US3_UF5.…”

Section: Lessons From Genomesmentioning

confidence: 99%

The Geobacillus paradox: why is a thermophilic bacterial genus so prevalent on a mesophilic planet?

2014

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The genus Geobacillus comprises endospore-forming obligate thermophiles. These bacteria have been isolated from cool soils and even cold ocean sediments in anomalously high numbers, given that the ambient temperatures are significantly below their minimum requirement for growth. Geobacilli are active in environments such as hot plant composts, however, and examination of their genome sequences reveals that they are endowed with a battery of sensors, transporters and enzymes dedicated to hydrolysing plant polysaccharides. Although they appear to be relatively minor members of the plant biomass-degrading microbial community, Geobacillus bacteria have achieved a significant population with a worldwide distribution, probably in large part due to adaptive features of their spores. First, their morphology and resistance properties enable them to be mobilized in the atmosphere and transported long distances. Second, their longevity, which in theory may be extreme, enables them to lie quiescent but viable for long periods of time, accumulating gradually over time to achieve surprisingly high population densities. Introduction: an environmental enigmaGeobacillus bacteria are rod-shaped, aerobic or facultatively anaerobic, endospore-forming microbes. Depending on the strain, the temperature range for growth can extend as low as 35 u C or as high as 80 u C. But for most isolates, temperatures between about 45 and 70 u C are required (Nazina et al., 2001). These characteristics make Geobacillus bacteria (geobacilli) attractive to the biotechnology industry as sources of thermostable enzymes (de Champdoré et al., 2007; Karagüler et al., 2007), as platforms for biofuel production (Cripps et al., 2009;Taylor et al., 2009) and as potential components of bioremediation strategies (Markossian et al., 2000;Obojska et al., 2002;Perfumo et al., 2007). Obligate thermophiles, however, face a significant challenge outside the lab: they must survive on a planet with an average annual land surface temperature that has only ranged between 7 and 10 uC over the past three centuries (Rohde et al., 2013). It would be logical to assume, then, that Geobacillus would only be found in substantial numbers in the warmest regions of the planet, such as equatorial deserts or naturally occurring geothermal and hydrothermal hotspots. The truth, however, is rather more complicated.As Fig. 1 illustrates, people have been able to detect Geobacillus nearly everywhere they have thought to look. (This figure is based on a survey of 146 mostly recent references describing the isolation of Geobacillus in natural or human-made environments; for full details, see Table S1, available in Microbiology Online.) One can see at a glance that these bacteria have been isolated from sources on all seven continents as well as the Pacific Ocean and the Mediterranean Sea. What may not be obvious from a twodimensional map is that there has been much diversity in the third dimension as well. Geobacillus has been isolated from the Bolivian Andes at an altitude of 3653 m (Ma...

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“…The structure-function relationships of many of its hemicellulolytic enzymes were investigated intensively (31)(32)(33)(34)(35)(36)(37)(38)(39) together with its arabinan-and galactandegrading systems (19,20). The bacterium possesses two-and three-component oligosaccharide-sensing systems that activate the expression of dedicated ABC sugar transporters (19 -22, 40), allowing the cell to rapidly respond to very low carbohydrates concentrations in the soil and to efficiently take up the oligosaccharides (20,21).…”

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confidence: 99%