# Azotobacter vinelandii gene fitness following carbon shift from sucrose to acetate, succinate and glycerol

## TL;DR

This study identifies essential genes in Azotobacter vinelandii for growth and nitrogen fixation when the carbon source is changed from sucrose to acetate, succinate, or glycerol.

## Contribution

The work expands understanding of A. vinelandii's essential genes under different carbon sources using transposon sequencing.

## Key findings

- Genes essential for central metabolism and substrate processing were identified.
- Some unexpected genes were found to be critical for growth on specific carbon sources.
- The study provides insights into A. vinelandii's metabolic flexibility for nitrogen fixation.

## Abstract

Nitrogen-fixing microbes are a primary contributor of this important nutrient to the global nitrogen cycle. Biological nitrogen fixation (BNF) through the enzyme nitrogenase requires extensive energy that in whole cells is generally studied during the oxidation of carbohydrates such as sugars. The nitrogen-fixing bacterium Azotobacter vinelandii is a model diazotroph for the study of aerobic BNF. Much is known about metabolism in A. vinelandii when cultured on a simple medium where energy is provided primarily in the form of sucrose or glucose. Outside of the laboratory, this soil bacterium grows on metabolites primarily derived from plant root exudates or from the degradation of dead plant matter. In this work, we expand on previous studies looking at genes that are essential to BNF in A. vinelandii when grown on sucrose medium using transposon sequencing (Tn-seq). We applied Tn-seq to determine the genes essential to growth when the medium was shifted to acetate, succinate or glycerol as the primary carbon and energy source to fuel both growth and BNF. A global overview of the genes of central metabolism and those directing substrates toward central metabolism, along with a selection of unexpected genes that were essential for specific growth substrates, is provided.