Polymer degrading marine Microbulbifer bacteria: an un(der)utilized source of chemical and biocatalytic novelty

Abstract

Microbulbifer is a genus of halophilic bacteria that are commonly detected in the commensal marine microbiomes. These bacteria have been recognized for their ability to degrade polysaccharides and other polymeric materials. Increasingly, Microbulbifer genomes indicate these bacteria to be an untapped reservoir for novel natural product discovery and biosynthetic novelty. In this review, we summarize the distribution of Microbulbifer bacteria, activities of the various polymer degrading enzymes that these bacteria produce, and an up-to-date summary of the natural products that have been isolated from Microbulbifer strains. We argue that these bacteria have been hiding in plain sight, and contemporary efforts into their genome and metabolome mining are going to lead to a proliferation of Microbulbifer-derived natural products in the future. We also describe, where possible, the ecological interactions of these bacteria in marine microbiomes.

Keywords: bacteria; hydrolases; marine natural products.

Figure 1

Oceanic distribution and marine holobiont sources of Microbulbifer strains described in the literature.

Figure 2

The chemical structure of agarose with the key β-1,4 linkage denoted.

Figure 3

The chemical structure of the biopolymer alginate.

Figure 4

The chemical structure of chitin.

Figure 5

Chemical structures of sulfated polysaccharides κ-, ι-, and λ-carrageenans.

Figure 6

Chemical structures of 4HBA (1) and parabens (2–14) isolated from Microbulbifer strains, and synthetic analogus (15–17).

Figure 7

Chemical structures of nucleosides 18–20 isolated from Microbulbifer strains.

Figure 8

Chemical structures of alkaloids 21–24 isolated from Microbulbifer strains.

Figure 9

Chemical structures of (2Z,4E)-3-methyl-2,4-decadienoic acid (25) and 4-BP (26) natural products isolated from Microbulbifer strains.

Figure 10

Chemical structures of bulbiferamides 27–30 and pseudobulbiferamides 31–35.

Figure 11

Proposed NRPS assembly lines for the biosynthesis of (A) bulbiferamide A (27) and (B) pseudobulbiferamide A (31).

Figure 12

Chemical structures of 2-heptyl-1H-quinolin-4-one (36, HHQ), 2-heptyl-1-hydroxyquinolin-4-one (37, HQHO), and their brominated products BrHHQ 38 and BrHQHO 39.