Differential gene expression of Pectinatus frisingensis TMW 2.2471 under beer associated stresses

Beer spoilage causes huge economic losses for the brewing industry. Only a few obligate anaerobic bacteria are capable of growing in beer. They can spoil the batches after brewing and during maturation, thereby causing especially serious damage. Pectinatus frisingensis is one of the most dreaded species of anaerobic beer spoilers. It causes turbidity and acidity as well as off flavors. While the growth-limiting stressors of beer have been well studied, the underlying mechanisms of adaptation are still largely unknown. A transcriptional study was conducted on P. frisingensis TMW 2.2471 by exposing it to ethanol stress of 4.76% (v/v) and acid stress at pH 4.04 separately. Both experiments were executed in alcohol free beer (AFB) and peptone yeast extract glucose medium (PYG). The transcriptomic responses of P. frisingensis strain TMW 2.2471 to ethanol and acid stress showed several differently upregulated genes. P. frisingensis reacted to both stressors by upregulating heat shock protein 20 and UvrABC endonuclease for repair processes. Ethanol stress additionally caused the upregulation of co-chaperone GroES and Clp protease, while expressing acetolactate synthase and decarboxylase only under acid stress. Our findings suggest that P. frisingensis is capable of a broad response in an unexpectedly large number of metabolic functions. Its survival is based on combining universal and exclusive stress responses to ethanol and acid stress, the two main stressors presented by beer.