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Sugars are everywhere and involved in all biological processes! We live in a complex ecosystem where humans comprise only a small part of that environment. Bacteria have come to the forefront of most scientific studies as numerous microbiome comparisons link certain microorganisms, or specific metabolic traits, or the diversity/ uniformity in community structure with various states of health and disease. More and more, it is realized that sugars are at the apex of these interactions. This is not unanticipated since carbohydrates are associated with every macromolecule of life (nucleic acids, lipids and proteins) and themselves comprise the most complex class of macromolecules through the limitless structures that are found in nature, coupled with the numerous options for joining these monosaccharides together (alpha or beta linkages, linear or branched chains, connected through varying carbon positions, and modified with an endless repertoire of substituents). All bacteria are capable of synthesizing a unique inventory of glycoconjugate structures on their surfaces that play key biological roles ranging from host mimicry to bacteriophage evasion. We now recognize that bacteria are also capable of modifying their proteins with sugars using traditional pathways for N- and O-linked glycoprotein biosynthesis similar to their eukaryotic counterparts, but have also devised novel methods for protein modification with permutations in these pathways. Although the diversity and boundless possibilities for carbohydrate structures that can be created by bacteria at times seems overwhelming, there are common principles for glycoconjugate biosynthesis that guide us in discovering and exploiting these pathways. Similarly, bacterial viruses (bacteriophages) are the most abundant biological entity on earth, estimated to outnumber bacteria 10:1, and reaching up to 10+31 in number. Therefore, understanding how phages influence bacterial communities and behavior will be instrumental in understanding the microbiome data that are being generated. Bacteriophages, many of which specifically recognize their hosts through the unique surface glycoconjugates that they display, also represent a lucrative resource for exploitation, especially in the area of glycomics.
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