Proteomic Analysis of the Xanthan-Degrading Pathway of <i>Microbacterium</i> sp. XT11

Sun, Zhen; Liu, Huixue; Wang, Xueyan; Yang, Fan; Li, Xianzhen

doi:10.1021/acsomega.9b02313

Cited by 8 publications

(9 citation statements)

References 34 publications

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“…This could be due to fast depolymerization and cellular importation of the XG polymer following lyase removal of the terminal mannose. Alternatively, the data are also consistent with a degradation model in which the XG backbone is cleaved prior to subsequent hydrolysis of the repeating pentasaccharide, a pathway that has not been characterized in XGdegrading bacteria and might result in pentasaccharides with full linkage complexity being transported into the bacterial cell before depolymerization 27,28 .…”

Section: Bacteroides Intestinalissupporting

confidence: 79%

Mechanistic insights into consumption of the food additive xanthan gum by the human gut microbiota

et al. 2022

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The diets of industrialized countries reflect the increasing use of processed foods, often with the introduction of novel food additives. Xanthan gum is a complex polysaccharide with unique rheological properties that have established its use as a widespread stabilizer and thickening agent 1 . However, little is known about its direct interaction with the gut microbiota, which plays a central role in digestion of other, chemically-distinct dietary fiber polysaccharides. Here, we show that the ability to digest xanthan gum is surprisingly common in industrialized human gut microbiomes and appears to be contingent on the activity of a single bacterium that is a member of an uncultured bacterial genus in the family Ruminococcaceae. We used a combination of enrichment culture, multi-omics, and recombinant enzyme studies to identify and characterize a complete pathway in this uncultured bacterium for the degradation of xanthan gum. Our data reveal that this keystone degrader cleaves the xanthan gum backbone with a novel glycoside hydrolase family 5 (GH5) enzyme before processing the released oligosaccharides using additional enzymes. Surprisingly, some individuals harbor a Bacteroides species that is capable of consuming oligosaccharide products generated by the keystone Ruminococcaceae or a purified form of the GH5 enzyme. This Bacteroides symbiont is equipped with its own distinct enzymatic pathway to cross-feed on xanthan gum breakdown products, which still harbor the native linkage complexity in xanthan gum, but it cannot directly degrade the high molecular weight polymer. Thus, the introduction of a common food additive into the human diet in the past 50 years has promoted the establishment of a food chain involving at least two members of different phyla of gut bacteria.

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Section: Bacteroides Intestinalissupporting

confidence: 79%

Mechanistic insights into consumption of the food additive xanthan gum by the human gut microbiota

et al. 2022

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show abstract

“…This could be due to fast depolymerization and cellular importation of the XG polymer following lyase removal of the terminal mannose. Alternatively, the data are also consistent with a degradation model in which the XG backbone is cleaved prior to subsequent hydrolysis of the repeating pentasaccharide, a pathway that has not been characterized in XG-degrading bacteria and might result in pentasaccharides with full linkage complexity being transported into the bacterial cell before depolymerization 27,28 .…”

Section: Introductionsupporting

confidence: 80%

The Food Additive Xanthan Gum Drives Adaptation of the Human Gut Microbiota

Ostrowski

Rosa

Kunath

et al. 2021

Preprint

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The diets of industrialized countries reflect the increasing use of processed foods, often with the introduction of novel food additives. Xanthan gum is a complex polysaccharide with unique rheological properties that have established its use as a widespread stabilizer and thickening agent. However, little is known about its direct interaction with the gut microbiota, which plays a central role in digestion of other, chemically-distinct dietary fiber polysaccharides. Here, we show that the ability to digest xanthan gum is surprisingly common in industrialized human gut microbiomes and appears to be contingent on the activity of a single bacterium that is a member of an uncultured bacterial genus in the family Ruminococcaceae. We used a combination of enrichment culture, multi-omics, and recombinant enzyme studies to identify and characterize a complete pathway in this uncultured bacterium for the degradation of xanthan gum. Our data reveal that this keystone degrader cleaves the xanthan gum backbone with a novel glycoside hydrolase family 5 (GH5) enzyme before processing the released oligosaccharides using additional enzymes. Surprisingly, some individuals harbor a Bacteroides species that is capable of consuming oligosaccharide products generated by the keystone Ruminococcaceae or a purified form of the GH5 enzyme. This Bacteroides symbiont is equipped with its own distinct enzymatic pathway to cross-feed on xanthan gum breakdown products, which still harbor the native linkage complexity in xanthan gum, but it cannot directly degrade the high molecular weight polymer. Thus, the introduction of a common food additive into the human diet in the past 50 years has promoted the establishment of a food chain involving at least two members of different phyla of gut bacteria.

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“…Proteins (ID_01096, 00605 and 02737), putatively a β-xylanase, a cyclomaltodextrinase and a cyclodextrin-binding protein, respectively, are also related to carbohydrate metabolism but not obviously linked to xanthan degradation, but rather to degradation of the hemicellulose xylan and of cyclodextrins, which are oligosaccharides derived from starch. During growth on xanthan, the provision of transport systems for the uptake of xanthan breakdown products can be expected ( Sun et al, 2019 ). Indeed, further secretome proteins induced during growth on xanthan included the putative transport proteins ID_05266 and 05267.…”

Section: Discussionmentioning

confidence: 99%

Identification of a novel xanthan-binding module of a multi-modular Cohnella sp. xanthanase

Han,

Baudrexl,

Ludwig

et al. 2024

Front. Microbiol.

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A new strain of xanthan-degrading bacteria identified as Cohnella sp. has been isolated from a xanthan thickener for food production. The strain was able to utilize xanthan as the only carbon source and to reduce the viscosity of xanthan-containing medium during cultivation. Comparative analysis of the secretomes of Cohnella sp. after growth on different media led to the identification of a xanthanase designated as CspXan9, which was isolated after recombinant production in Escherichia coli. CspXan9 could efficiently degrade the β-1,4-glucan backbone of xanthan after previous removal of pyruvylated mannose residues from the ends of the native xanthan side chains by xanthan lyase treatment (XLT-xanthan). Compared with xanthanase from Paenibacillus nanensis, xanthanase CspXan9 had a different module composition at the N- and C-terminal ends. The main putative oligosaccharides released from XLT-xanthan by CspXan9 cleavage were tetrasaccharides and octasaccharides. To explore the functions of the N- and C-terminal regions of the enzyme, truncated variants lacking some of the non-catalytic modules (CspXan9-C, CspXan9-N, CspXan9-C-N) were produced. Enzyme assays with the purified deletion derivatives, which all contained the catalytic glycoside hydrolase family 9 (GH9) module, demonstrated substantially reduced specific activity on XLT-xanthan of CspXan9-C-N compared with full-length CspXan9. The C-terminal module of CspXan9 was found to represent a novel carbohydrate-binding module of family CBM66 with binding affinity for XLT-xanthan, as was shown by native affinity polyacrylamide gel electrophoresis in the presence of various polysaccharides. The only previously known binding function of a CBM66 member is exo-type binding to the non-reducing fructose ends of the β-fructan polysaccharides inulin and levan.

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Proteomic Analysis of the Xanthan-Degrading Pathway of Microbacterium sp. XT11

Cited by 8 publications

References 34 publications

Mechanistic insights into consumption of the food additive xanthan gum by the human gut microbiota

Mechanistic insights into consumption of the food additive xanthan gum by the human gut microbiota

The Food Additive Xanthan Gum Drives Adaptation of the Human Gut Microbiota

Identification of a novel xanthan-binding module of a multi-modular Cohnella sp. xanthanase

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