Transcriptomic and Metabolomic Analysis of a Fusidic Acid-Selected fusA Mutant of Staphylococcus aureus

Sushim K Gupta; Richard F Pfeltz; Brian J Wilkinson; John E Gustafson

doi:10.3390/antibiotics11081051

Transcriptomic and Metabolomic Analysis of a Fusidic Acid-Selected fusA Mutant of Staphylococcus aureus

Antibiotics (Basel). 2022 Aug 3;11(8):1051. doi: 10.3390/antibiotics11081051.

Authors

Sushim K Gupta¹, Richard F Pfeltz², Brian J Wilkinson³, John E Gustafson^{1

4}

Affiliations

¹ Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
² BD Life Sciences, Microbiology Research and Development, Sparks, MD 21152, USA.
³ School of Biological Sciences, Illinois State University, Normal, IL 61761, USA.
⁴ Department of Biology, New Mexico State University, Las Cruces, NM 88003, USA.

Abstract

Physiological experimentation, transcriptomics, and metabolomics were engaged to compare a fusidic acid-resistant Staphylococcus aureus mutant SH10001st-2 to its parent strain SH1000. SH10001st-2 harbored a mutation (H457Y) in the gene fusA which encodes the fusidic acid target, elongation factor G, as well as mutations in a putative phage gene of unknown function. SH10001st-2 grew slower than SH1000 at three temperatures and had reduced coagulase activity, two indicators of the fitness penalty reported for fusA-mediated fusidic acid- resistance in the absence of compensatory mutations. Despite the difference in growth rates, the levels of O₂ consumption and CO₂ production were comparable. Transcriptomic profiling revealed 326 genes were upregulated and 287 were downregulated in SH10001st-2 compared to SH1000. Cell envelope and transport and binding protein genes were the predominant functional categories of both upregulated and downregulated genes in SH10001st-2. Genes of virulence regulators, notably the agr and kdp systems, were highly upregulated as were genes encoding capsule production. Contrary to what is expected of mid-exponential phase cells, genes encoding secreted virulence factors were generally upregulated while those for adhesion-associated virulence factors were downregulated in SH10001st-2. Metabolomic analysis showed an overall increase in metabolite pools in SH10001st-2 compared to SH1000, mostly for amino acids and sugars. Slowed growth and metabolite accumulation may be byproducts of fusA mutation-mediated protein synthesis impairment, but the overall results indicate that SH10001st-2 is compensating for the H457Y fitness penalty by repurposing its virulence machinery, in conjunction with increasing metabolite uptake capacity, in order to increase nutrient acquisition.

Keywords: Staphylococcus aureus; fusidic acid-resistance; metabolomics; respiration; transcriptional profiling.

Grants and funding

We wish to acknowledge support from the National Institutes of Health: S06 GM008136-32 (J. E. G., NMSU SCORE PROGRAM); S06 GM61222-05 (A. D., NMSU-MBRS-RISE PROGRAM); and P20RR016480 from the NM-INBRE Program of the National Center for Research Resources. This work was also supported by the Oklahoma Agricultural Experiment Station.