Future Directions of Marine Myxobacterial Natural Product Discovery Inferred from Metagenomics

Abstract

Over the last two decades, halophilic (organisms that thrive at high salt concentrations) and halotolerant (organisms that have adapted to high salt concentrations) myxobacteria emerged as an important source of structurally diverse secondary metabolites from the marine environment. This review explores the advance of metagenomics analysis and 16S rRNA gene phylogeny of the cultured and uncultured myxobacteria from marine and other salt-environments up to July 2018. The diversity of novel groups of myxobacteria in these environments appears unprecedented, especially in the Sorangiineae and Nannocystineae suborders. The Sandaracinaceae related clade in the Sorangiineae suborder seems more widely distributed compared to the exclusively marine myxobacterial cluster. Some of the previously identified clones from metagenomic studies were found to be related to the Nannocystineae suborder. This understanding provides the foundation for a vital, unexplored resource. Understanding the conditions required to cultivate these yet “uncultured” myxobacteria in the laboratory, while a key next step, offers a significant potential to further expand access to diverse secondary metabolites.

Comparative Genomics and Pan-Genomics of the Myxococcaceae, including a Description of Five Novel Species: Myxococcus eversor sp. nov., Myxococcus llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogochensis sp. nov., Myxococcus vastator sp. nov., Pyxidicoccus caerfyrddinensis sp. nov., and Pyxidicoccus trucidator sp. nov.

“…Marine myxobacteria isolates are often novel taxonomically and produce diverse and unusual bioactive molecules ( Amiri Moghaddam et al. 2018 ; Garcia et al. 2018 ).…”

Both Soil Bacteria and Soil Chemical Property Affected the Micropredator Myxobacterial Community: Evidence from Natural Forest Soil and Greenhouse Rhizosphere Soil

“…However, the general conclusion that Cystobacterineae could be supported more efficiently by Gram-negative preys still needs more evidence. It is not known whether myxobacteria from Nannocystineae suborder can prey on bacteria, but these taxa are known for agar degradation [ 54 ]. Haliangiaceae from Nannocystineae was shown to be efficiently supported by Arthrobacter globiformis , a Gram-positive actinobacteria [ 53 ].…”

Metabolic and Biosynthetic Diversity in Marine Myxobacteria

“…M. xanthus HW-1 attracted our attention particularly because all except for one biosynthetic gene cluster (22 of 23) encoded in its genome sequence could also be found in the related M. macrosporus DSM 14697 [ 77 ] isolated from soil. This close similarity between these two strains is also reflected in the 16S rRNA gene sequence showing their clustering in the phylogenetic tree [ 78 ]. The substantial overlap of biosynthetic gene cluster profiles between two Myxococci raises the question whether such very similar strains can grow under such different conditions, such as soil and saline water, or if such strains are more versatile and can thrive in both ecological niches.…”