Insights into the molecular basis of c-di-GMP signalling in Pseudomonas aeruginosa.

The opportunistic human pathogen Pseudomonas aeruginosa can cause severe infections in immunocompromized people or cystic fibrosis (CF) patients. Because of its remarkable ability to invade the host and withstand the bacteriocidal effect of most conventional antibiotics, the infection caused by P. aeruginosa has become a major concern for human health. The switch from acute to chronic infection is governed by the second messenger bis-(3'-5')-cyclic dimeric guanosine mono-phosphate (c-di-GMP) in P. aeruginosa, and c-di-GMP is now recognized to regulate many important biological processes in pathogenesis. The c-di-GMP signalling mechanisms in P. aeruginosa have been studied extensively in the past decade, revealing complicated c-di-GMP metabolism and signalling network. In this review, the underlying mechanisms of this signalling network will be discussed, mainly focussing on how environmental cues regulate c-di-GMP signalling, protein-protein interaction mediated functional regulation, heterogeneity of c-di-GMP and cross talk between c-di-GMP signalling and other signalling systems. Understanding the molecular mechanism underlying the complex c-di-GMP signalling network would be beneficial for developing therapeutic approaches and antibacterial agents to combat the threat from P. aeruginosa.

Discovering novel biomarkers for diagnosis and treatment monitoring of active pulmonary tuberculosis by ion metabolism analysis.

Tuberculosis (TB) is a highly lethal infectious disease that poses a global threat. Timely and accurate biomarker for TB diagnosis and treatment monitoring remains a pressing need. Ions, the crucial trace element for humans, may be potential targets for TB diagnosis and the forecasting of TB development. To explore the potential of ions as biomarkers, we measured and compared the levels of various ions in whole blood and plasma samples from healthy control (HC), pulmonary TB patients (TB), cured pulmonary TB patients (RxTB), and other non-TB pneumonia patients (PN) by using ultra-high performance liquid chromatography-tandem mass spectrometry. Our study demonstrated that Cu (AUC = 0.670), Pb (AUC = 0.660), and Zn (AUC = 0.701) in whole blood exhibited promising diagnostic performance for TB. Then we used a neural network (NNET) for TB prediction, the AUC values used to differentiate definite TB from HC or PN in plasma were 0.867 and 0.864, respectively. The AUC values used to differentiate definite TB from HC or PN in whole blood were 0.818 and 0.660, respectively. Our correlation analysis showed that Zn (r= 0.356, p=0.001) and Cu (r= 0.361, p=0.0004) in plasma are most closely related to disease severity. Additionally, six ions (Cu, Sb, V, Mn, Fe, Sr) in plasma and whole blood were altered following anti-TB therapy. These results showed that ions could be diagnostic biomarkers for TB. Furthermore, the level of particular ions can forecast the degree of lung damage and the success of the TB treatment. In conclusion, this study highlights the possibility of using ions from blood samples to enable rapid tuberculosis diagnosis.

Roadmap for ending TB in China by 2035: The challenges and strategies.

Tuberculosis (TB) is one of the top ten causes of death worldwide, taking the lives of over a million people annually. In addition to being a serious health issue, TB is also closely linked to eradicating poverty according to the Sustainable Development Goals (SDGs) of the United Nations (UN). All UN members have committed to ending the TB epidemic by 2030. China has one of the highest TB loads worldwide, ranking third in the world on many TB burden indices. The national strategy for TB control is aimed at creating a collaborative network and integrating TB treatment into the medical system. According to the WHO's global TB report, China is expected to have 748,000 new cases of TB in 2022 and an incidence of 52 cases per 100,000 people. Ending TB remains a huge challenge and requires comprehensive control strategies in China. In this work, we have discussed the challenges of TB prevention and control in China and proposed specific measures to end TB.

Suppressing host pyroptosis by a ubiquitin-activated phospholipid phosphatase of Mycobacterium tuberculosis.

Tuberculosis (TB) is a major public health problem that causes millions of deaths in humans around the world, and the bacterial pathogen Mycobacterium tuberculosis (Mtb) is responsible for this disease. Evidence suggested that the inflammasome-pyroptosis pathway is crucial for preventing Mtb infection. Uncertainty exists regarding whether and how these infections can bypass this immune system by Mtb. A recent Science article by Chai et al. (doi: 10.1126/science.abq0132) revealed a novel role by a eukaryotic-like effector called PtpB during Mtb infection. The PtpB functions as a phospholipid phosphatase suppressing gasdermin D (GSDMD) dependent pyroptosis. And notably, the phospholipid phosphatase activity of PtpB is dependent on binding with mono-ubiquitin (Ub) of the host.

Microevolution of the mexT and lasR Reinforces the Bias of Quorum Sensing System in Laboratory Strains of Pseudomonas aeruginosa PAO1.

The Pseudomonas aeruginosa strain PAO1 has routinely been used as a laboratory model for quorum sensing (QS). However, the microevolution of P. aeruginosa laboratory strains resulting in genetic and phenotypic variations have caused inconsistencies in QS research. To investigate the underlying causes of these variations, we analyzed 5 Pseudomonas aeruginosa PAO1 sublines from our laboratory using a combination of phenotypic characterization, high throughput genome sequencing, and bioinformatic analysis. The major phenotypic variations among the sublines spanned across the levels of QS signals and virulence factors such as pyocyanin and elastase. Furthermore, the sublines exhibited distinct variations in motility and biofilm formation. Most of the phenotypic variations were mapped to mutations in the lasR and mexT, which are key components of the QS circuit. By introducing these mutations in the subline PAO1-E, which is devoid of such mutations, we confirmed their influence on QS, virulence, motility, and biofilm formation. The findings further highlight a possible divergent regulatory mechanism between the LasR and MexT in the P. aeruginosa. The results of our study reveal the effects of microevolution on the reproducibility of most research data from QS studies and further highlight mexT as a key component of the QS circuit of P. aeruginosa.

Regulation of Exopolysaccharide Production by ProE, a Cyclic-Di-GMP Phosphodiesterase in Pseudomonas aeruginosa PAO1.

The ubiquitous second messenger c-di-GMP is involved in regulation of multiple biological functions including the important extracellular matrix exopolysaccharides (EPS). But how c-di-GMP metabolic proteins influence EPS and their enzymatic properties are not fully understood. Here we showed that deletion of proE, which encodes a protein with GGDEF-EAL hybrid domains, significantly increased the transcriptional expression of the genes encoding EPS production in Pseudomonas aeruginosa PAO1 and changed the bacterial colony morphology. Our data showed that ProE is a very active phosphodiesterase (PDE), with a high enzyme activity in degradation of c-di-GMP. Interestingly, the optimal activity of ProE was found in the presence of Co2+, unlike other PDEs that commonly rely on Mg2+ or Mn2+ for best performance. Furthermore, we identified three widely conserved novel residues that are critical for the function of ProE through site-directed mutagenesis. Subsequent study showed that ProE, together with other three key PDEs, i.e., RbdA, BifA, and DipA regulate the EPS production in P. aeruginosa PAO1. Moreover, by using the GFP-fusion approach, we observed that these four EPS associated-PDEs showed a polar localization pattern in general. Taken together, our data unveil the molecular mechanisms of ProE in regulation of EPS production, and provide a new insight on its enzymatic properties in degradation of c-di-GMP.