Environmental phosphate differentially affects virulence phenotypes of uropathogenic Escherichia coli isolates causative of prostatitis

Inorganic phosphate modifies stationary phase fitness and metabolic pathways in Lactiplantibacillus paraplantarum CRL 1905

Inorganic phosphate (Pi) concentration modulates polyphosphate (polyP) levels in diverse bacteria, affecting their physiology and survival. Lactiplantibacillus paraplantarum CRL 1905 is a lactic acid bacterium isolated from quinoa sourdough with biotechnological potential as starter, for initiating fermentation processes in food, and as antimicrobial-producing organism. The aim of this work was to evaluate the influence of the environmental Pi concentration on different physiological and molecular aspects of the CRL 1905 strain. Cells grown in a chemically defined medium containing high Pi (CDM + P) maintained elevated polyP levels up to late stationary phase and showed an enhanced bacterial survival and tolerance to oxidative stress. In Pi sufficiency condition (CDM-P), cells were ~ 25% longer than those grown in CDM + P, presented membrane vesicles and a ~ 3-fold higher capacity to form biofilm. Proteomic analysis indicated that proteins involved in the "carbohydrate transport and metabolism" and "energy production and conversion" categories were up-regulated in high Pi stationary phase cells, implying an active metabolism in this condition. On the other hand, stress-related chaperones and enzymes involved in cell surface modification were up-regulated in the CDM-P medium. Our results provide new insights to understand the CRL 1905 adaptations in response to differential Pi conditions. The adjustment of environmental Pi concentration constitutes a simple strategy to improve the cellular fitness of L. paraplantarum CRL 1905, which would benefit its potential as a microbial cell factory.

Transcriptional Responses of Herbaspirillum seropedicae to Environmental Phosphate Concentration

Herbaspirillum seropedicae is a nitrogen-fixing endophytic bacterium associated with important cereal crops, which promotes plant growth, increasing their productivity. The understanding of the physiological responses of this bacterium to different concentrations of prevailing nutrients as phosphate (Pi) is scarce. In some bacteria, culture media Pi concentration modulates the levels of intracellular polyphosphate (polyP), modifying their cellular fitness. Here, global changes of H. seropedicae SmR1 were evaluated in response to environmental Pi concentrations, based on differential intracellular polyP levels. Cells grown in high-Pi medium (50 mM) maintained high polyP levels in stationary phase, while those grown in sufficient Pi medium (5 mM) degraded it. Through a RNA-seq approach, comparison of transcriptional profiles of H. seropedicae cultures revealed that 670 genes were differentially expressed between both Pi growth conditions, with 57% repressed and 43% induced in the high Pi condition. Molecular and physiological analyses revealed that aspects related to Pi metabolism, biosynthesis of flagella and chemotaxis, energy production, and polyhydroxybutyrate metabolism were induced in the high-Pi condition, while those involved in adhesion and stress response were repressed. The present study demonstrated that variations in environmental Pi concentration affect H. seropedicae traits related to survival and other important physiological characteristics. Since environmental conditions can influence the effectiveness of the plant growth-promoting bacteria, enhancement of bacterial robustness to withstand different stressful situations is an interesting challenge. The obtained data could serve not only to understand the bacterial behavior in respect to changes in rhizospheric Pi gradients but also as a base to design strategies to improve different bacterial features focusing on biotechnological and/or agricultural purposes.

Phosphate deficiency induced biofilm formation of Burkholderia on insoluble phosphate granules plays a pivotal role for maximum release of soluble phosphate

Involvement of biofilm formation process during phosphate (P) solubilization by rhizobacterial strains is not clearly understood. Scanning electron microscopic observations revealed prominent biofilm development on tricalcium phosphate as well as on four different rock phosphate granules by two P solubilizing rhizobacteria viz. Burkholderia tropica P4 and B. unamae P9. Variation in the biofilm developments were also observed depending on the total P content of insoluble P used. Biofilm quantification suggested a strong correlation between the amounts of available P and degrees of biofilm formation. Lower concentrations of soluble P directed both the organisms towards compact biofilm development with maximum substratum coverage. Variation in the production of extracellular polymeric substances (EPS) in the similar pattern also suggested its close relationship with biofilm formation by the isolates. Presence of BraI/R quorum sensing (QS) system in both the organisms were detected by PCR amplification and sequencing of two QS associated genes viz. braR and rsaL, which are probably responsible for biofilm formation during P solubilization process. Overall observations help to hypothesize for the first time that, biofilm on insoluble P granules creates a close environment for better functioning of organic acids secreted by Burkholderia strains for maximum P solubilization during P deficient conditions.

Intracellular Polyphosphate Levels in Gluconacetobacter diazotrophicus Affect Tolerance to Abiotic Stressors and Biofilm Formation

Gluconacetobacter diazotrophicus is a plant growth-promoting bacterium that is used as a bioinoculant. Phosphate (Pi) modulates intracellular polyphosphate (polyP) levels in Escherichia coli, affecting cellular fitness and biofilm formation capacity. It currently remains unclear whether environmental Pi modulates polyP levels in G. diazotrophicus to enhance fitness in view of its technological applications. In high Pi media, cells accumulated polyP and degraded it, thereby improving survival, tolerance to environmental stressors, biofilm formation capacity on abiotic and biotic surfaces, and competence as a growth promoter of strawberry plants. The present results support the importance of Pi and intracellular polyP as signals involved in the survival of G. diazotrophicus.

Effect of Tripterygium Wilfordii Polyglycoside on Experimental Prostatitis Caused by Ureaplasma Urealyticum in Rats

Background

Prostatitis is a common and refractory urological disease with complicated etiology. Ureaplasma urealyticum (UU) has a close relationship with human urinary tract infection that can induce nonbacterial prostatitis. Tripterygium wilfordii polyglycoside (TWP) is a non-steroidal immune inhibitor that causes significant immune suppression and anti-inflammatory effects. Its role in prostatitis caused by UU has not yet been established. The aim of this study was to investigate the effect of TWP on UU-infected prostatitis in a rat model.

Material/Methods

UU-infected prostatitis SD model rats were randomly divided into 2 groups: the prostatitis group (model group) and the TWP treatment group (treatment group). At 7 days after treatment, prostate weight, leucocyte count, lecithin corpuscles, UU infection rate, and UU microbe count were compared between the 2 groups. Serum inflammatory cytokines TNF-α was determined by ELISA, and ICAM-1 and NF-κB expression were detected.

Results

UU infection rate was 80% after modeling. The rat prostate weight and leucocyte count in the model group increased significantly, while lecithin corpuscles decreased. Compared with controls, inflammatory factor TNF-α, ICAM-1, and NF-κB expression were obviously higher (P<0.05). TWP markedly reduced prostate weight and leucocyte count, increased lecithin corpuscles, and decreased UU microbe count and TNF-α, ICAM-1, and NF-κB expression (P<0.05).

Conclusions

TWP can inhibit expression of inflammatory factors and may be useful in treating UU-infected prostatitis through reducing UU infection rate.

PhoB activation in non-limiting phosphate condition by the maintenance of high polyphosphate levels in the stationary phase inhibits biofilm formation in Escherichia coli

Polyphosphate (polyP) degradation in Escherichia coli stationary phase triggers biofilm formation via the LuxS quorum sensing system. In media containing excess of phosphate (Pi), high polyP levels are maintained in the stationary phase with the consequent inhibition of biofilm formation. The transcriptional-response regulator PhoB, which is activated under Pi limitation, is involved in the inhibition of biofilm formation in several bacterial species. In the current study, we report, for the first time, we believe that E. coli PhoB can be activated in non-limiting Pi conditions, leading to inhibition of biofilm formation. In fact, PhoB was activated when high polyP levels were maintained in the stationary phase, whereas it remained inactive when the polymer was degraded or absent. PhoB activation was mediated by acetyl phosphate with the consequent repression of biofilm formation owing to the downregulation of c-di-GMP synthesis and the inhibition of autoinducer-2 production. These results allowed us to propose a model showing that PhoB is a component in the signal cascade regulating biofilm formation triggered by fluctuations of polyP levels in E. coli cells during stationary phase.