A Complex Network of Sigma Factors and sRNA StsR Regulates Stress Responses in R. sphaeroides

Abstract

Adaptation of bacteria to a changing environment is often accompanied by remodeling of the transcriptome. In the facultative phototroph Rhodobacter sphaeroides the alternative sigma factors RpoE, RpoHI and RpoHII play an important role in a variety of stress responses, including heat, oxidative stress and nutrient limitation. Photooxidative stress caused by the simultaneous presence of chlorophylls, light and oxygen is a special challenge for phototrophic organisms. Like alternative sigma factors, several non-coding sRNAs have important roles in the defense against photooxidative stress. RNAseq-based transcriptome data pointed to an influence of the stationary phase-induced StsR sRNA on levels of mRNAs and sRNAs with a role in the photooxidative stress response. Furthermore, StsR also affects expression of photosynthesis genes and of genes for regulators of photosynthesis genes. In vivo and in vitro interaction studies revealed that StsR, that is under control of the RpoHI and RpoHII sigma factors, targets rpoE mRNA and affects its abundance by altering its stability. RpoE regulates expression of the rpoHII gene and, consequently, expression of stsR. These data provide new insights into a complex regulatory network of protein regulators and sRNAs involved in defense against photooxidative stress and the regulation of photosynthesis genes.

RNase III participates in control of quorum sensing, pigmentation and oxidative stress resistance in Rhodobacter sphaeroides

“…Taken together, our RNA‐seq data cannot unequivocally explain the effect of RNase III on pigmentation. However, the formation of photosynthetic complexes includes many regulatory circuits (Eisenhardt et al, 2018, 2021; Mank et al, 2012; Reuscher & Klug, 2021) and its regulation is very complex and may also involve yet unknown factors.…”

“…In a conclusion, the increased survival rate of the rnc − mutant under tBOOH stress can probably not be explained solely by an elevated catalase level. Like the formation of photosynthesis complexes, the oxidative stress response of R. sphaeroides includes a complex network of different regulators (Eisenhardt et al, 2021).…”

“…We discovered several small regulatory RNAs (sRNAs) (Berghoff et al, 2009), which affect important physiological processes like, for example, growth and cell division (Grützner, Remes, et al, 2021), stress resistance (Adnan et al, 2015;Billenkamp et al, 2015;Müller et al, 2016;Peng et al, 2016) and formation of photosynthesis complexes (Eisenhardt et al, 2018;Mank et al, 2012; in the model organism Rhodobacter sphaeroides (recently renamed to Cereibacter sphaeroides, Hördt et al, 2020). R. sphaeroides is a gram-negative purple non-sulphur bacterium with versatile metabolism, able to live under a variety of different environmental conditions, which makes it a well-suited model to study adjustment of gene expression to changing environmental conditions.…”

The Regulatory Functions of the Multiple Alternative Sigma Factors RpoE, RpoHI, and RpoHII Depend on the Growth Phase in Rhodobacter sphaeroides

“…In bacteria, the processes are mainly regulated by alternative sigma factors, which can combine with RNA polymerase to recognize specific promoters in cells and quickly adjust gene expressions in response to various signal stimuli. Furthermore, additional levels of regulation, post-transcriptional regulation, and translational regulation have been revealed [36]. To date, the molecular mechanisms of gene regulation with respect to growth phases are only known in a few species.…”

Excess Escherichia elicits mild autism spectrum disorder in young subjects via disturbing the balance of gut microbial GABA metabolism

“…In addition, we identi ed a plethora of profoundly altered stress response genes which as a whole was signi cantly decreased in the hASD subjects (Figure 4D). Of note, some of these stress response genes, such as gor, gpx, sod1 and katG (Figure S4, Table S5), encode enzymes for detoxifying superoxidase and peroxide, which are primary intracellular reactions of microbes for overcoming extracellular stresses [48][49][50]. These data suggested a suboptimal living environment wherein the overall hypofunction of the hASDlinked GM community occurred.…”