Alternative Sigma Factor B in Bovine Mastitis-Causing Staphylococcus aureus: Characterization of Its Role in Biofilm Formation, Resistance to Hydrogen Peroxide Stress, Regulon Members

Abstract

This study examines treatments of the bacterial pathogen Staphylococcus aureus, namely, in the context of its being a major cause of subclinical bovine mastitis. Such infections caused by S. aureus among dairy cows are difficult to detect and can easily become chronic, leading to reduced productivity and large losses for dairy manufacturers. In this study, the role of alternative sigma factor B (σB), which has been shown to be a global regulator for S. aureus infections, was explored in a mastitis-causing S. aureus strain, RF122. For comparison with the wild-type strain, a sigB null (ΔsigB) mutant was constructed and analyzed for its phenotypes and transcriptome. Our study found that σB is essential for biofilm formation as the ΔsigB mutant strain produced significantly less biofilm than did the wild-type strain at 48 h. σB is involved in response to H2O2 stress. However, σB plays a minor or no role in resistance to antiseptics (e.g., povidone-iodine and chlorhexidine), resistance to tested antibiotics, hemolysin activity, and invasion ability. RNA sequencing identified 225 σB-dependent genes, of which 171 are positively regulated and 54 are negatively regulated. The identified genes are involved in stress response, pathogenesis, and metabolic mechanisms. Quantitative TaqMan RT-PCR was performed to verify the RNA sequencing results; i.e., σB is a positive regulator for asp23, sarA, katA, yabJ, sodA, SAB2006c, and nrdD expressions. In the RF122 strain, σB plays a role in biofilm formation, general stress response (e.g., H2O2), and regulation of virulence factors and virulence-associated genes.

Advanced Glycation End Products Enhance Biofilm Formation by Promoting Extracellular DNA Release Through sigB Upregulation in Staphylococcus aureus

“…This result suggested that the AGE-BSA promoted eDNA release possibly through the sigB–lrg pathway, in which sigB plays an important role. Sigma factor B is the key factor in the stress response system in S. aureus , closely related to drug resistance, toxin expression, and biofilm formation ( Supa-Amornkul et al, 2019 ). To further investigate the role of sigB in this process, biofilms produced by the Newman sigB- deficient mutant (Newman-Δ sigB ) grown in the presence of AGE-BSA or BSA were subjected to biofilm mass analysis.…”

“…Sigma factor B regulates biofilm formation by regulating various genes implicated in the onset and maintenance of biofilms ( Nicholas et al, 1999 ), including the icaADBC operon to affect PIA production, and other ica-independent genes such as clfA , hla , and cid/lrg to affect eDNA release ( Supa-Amornkul et al, 2019 ). qRT-PCR revealed that lrg transcription decreased significantly with the increase in sigB after AGE treatment.…”

Nanostructured N/S doped carbon dots/mesoporous silica nanoparticles and PVA composite hydrogel fabrication for anti-microbial and anti-biofilm application

“…Next, the wells were washed with 200 μL of tap water for two times to remove the excess staining and dried overnight. The crystal violet in the wells was dissolved with 200 μL of 30% acetic acid and measured at OD 560 by using the microplate reader (Cytation5 imaging reader, BioTek, USA) ( Supa-Amornkul et al, 2019 ).…”

Insight of Melatonin: The Potential of Melatonin to Treat Bacteria-Induced Mastitis

“…Factors associated with the development of mastitis include the physiological status of the animal [ 60 ], environmental hygiene [ 61 ], bacteria [ 62 ], and viruses [ 63 ], with bacteria regarded as the most frequent cause of mammary gland inflammation. The three major types of bacterial pathogens causing mastitis are Staphylococcus aureus , Escherichia coli and Streptococcus .…”