On the way toward regulatable expression systems in acetic acid bacteria: target gene expression and use cases

Philipp Moritz Fricke,Angelika Klemm,Michael Bott,Tino Polen

doi:10.1007/s00253-021-11269-z

Philipp Moritz Fricke, Angelika Klemm + Show 2 more

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https://doi.org/10.1007/s00253-021-11269-z

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Abstract

Acetic acid bacteria (AAB) are valuable biocatalysts for which there is growing interest in understanding their basics including physiology and biochemistry. This is accompanied by growing demands for metabolic engineering of AAB to take advantage of their properties and to improve their biomanufacturing efficiencies. Controlled expression of target genes is key to fundamental and applied microbiological research. In order to get an overview of expression systems and their applications in AAB, we carried out a comprehensive literature search using the Web of Science Core Collection database. The Acetobacteraceae family currently comprises 49 genera. We found overall 6097 publications related to one or more AAB genera since 1973, when the first successful recombinant DNA experiments in Escherichia coli have been published. The use of plasmids in AAB began in 1985 and till today was reported for only nine out of the 49 AAB genera currently described. We found at least five major expression plasmid lineages and a multitude of further expression plasmids, almost all enabling only constitutive target gene expression. Only recently, two regulatable expression systems became available for AAB, an N-acyl homoserine lactone (AHL)-inducible system for Komagataeibacter rhaeticus and an l-arabinose-inducible system for Gluconobacter oxydans. Thus, after 35 years of constitutive target gene expression in AAB, we now have the first regulatable expression systems for AAB in hand and further regulatable expression systems for AAB can be expected.Key points• Literature search revealed developments and usage of expression systems in AAB.• Only recently 2 regulatable plasmid systems became available for only 2 AAB genera.• Further regulatable expression systems for AAB are in sight.

Highlights

Acetic acid bacteria (AAB) are a group of obligately aerobic Gram-negative bacteria that exhibit a unique form of metabolism by which they typically partially oxidize a variety of substrates such as sugars or ethanol by membrane-bound dehydrogenases and produce acetic acid
Two regulatable expression systems, an N-acyl homoserine lactone-inducible luxR-Plux system for Komagataeibacter rhaeticus and an Larabinose-inducible araC-ParaBAD system for Gluconobacter oxydans with up to 480-fold induction have recently been reported for the two AAB species (Florea et al 2016a; Fricke et al 2020)
The Ga. liquefaciens group and the Ga. xylinus group could be phylogenetically, phenotypically and ecologically distinguished from each other at the generic level. This resulted in the creation of the new AAB genus Komagataeibacter based on 16S rRNA gene sequences and the transfer of several new combinations including Ga. xylinus to Komagataeibacter xylinus on the basis of taxonomic characteristics (Yamada 2014; Yamada et al 2012). Taking these AAB genera updates and renaming of AAB species into account for the publications before 1989, 1998, and 2014, we found in our final list 101 publications related to Gluconobacter, 61 to Komagataeibacter, 41 to Acetobacter, 20 to Gluconacetobacter, 8 to Acidiphilium, 6 to Acidomonas, 4 to Asaia, 1 to Kozakia, and 1 to Roseomonas, respectively

Summary

Introduction

Acetic acid bacteria (AAB) are a group of obligately aerobic Gram-negative bacteria that exhibit a unique form of metabolism by which they typically partially oxidize a variety of substrates such as sugars or ethanol by membrane-bound dehydrogenases (mDHs) and produce acetic acid. The broad-host-range vector pSUP104, which includes the mobilization and replication functions of the IncQ plasmid RSF1010 and was originally tested in Rhizobium, Agrobacterium, and Pseudomonas species, respectively, was used in Gluconobacter to complement a Tn5-based pqqE-deficient mutant by expressing a genomic library fragment containing the pqqE gene of the PQQ coenzyme biosynthesis gene cluster pqqBCDE of G. oxydans ATCC 9937 (Felder et al 2000).

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Conclusion