Isolation and algicidal properties study of the strain G1 from reservoir sediments

Microcystis aeruginosa is a globally important cyanobacterial species that poses a threat to human health and development. The use of bacteria to control algal blooms has become an important research topic in recent years. In the present work, the algicidal strain G1 was isolated from sediments of a reservoir in Xi'an, China, identified by 16S ribosomal DNA (rDNA), and its algicidal effects were investigated. The rDNA sequence of G1 (GenBank accession number MW205793) is 99.86% similar to that of Chitinimonas sp., and the strain indirectly solubilised algae. Algae removal by G1 was optimal during the decay phase (algae solubilisation rate = 65.85%). Temperature (5–120 °C) did not significantly affect algae removal, pH 5–9 was tolerated, and pH 7 achieved the highest algae lysis rate (63.56%). Ultrasonic treatment of G1 destroyed the algae-solubilising effect. An injection ratio of 15% achieved the highest algae lysis rate (67.64%) under 12 h:12 h light:dark conditions, and full darkness achieved the highest algae lysis rate (68.21%). Thus, G1 can effectively inhibit the reproduction of M. aeruginosa, making it a promising biological agent for controlling algal growth.

Study on the Efficiency of On-Site Sludge Reduction Using Ti/SnO2-Sb and Ti/RuO2-IrO2 Electrodes Based on a Cell Lysis-Cryptic Growth System

The present study investigated the parameters and the mechanism of action of electrochemical cell lysis to reduce the return sludge from secondary settlers based on the theory of cell lysis-cryptic growth. The factors influencing the functioning of two electrodes (Ti/SnO2-Sb and Ti/RuO2-IrO2) were investigated to determine the optimal cell lysis parameters for each electrode, and the effects of the two electrodes on cell lysis were compared under these conditions. Finally, the Ti/SnO2-Sb electrode was selected for the subsequent experiments. The electrolysis reaction was performed using the following parameters: the initial sludge concentration was 7000 mg/L, the working voltage was 18 V, the plate spacing was 1 cm, the initial pH was 6.8 to 7.0, and the electrolysis duration was 90 min. The degree of disintegration of the sludge and the cell lysis rate reached 25.35% and 20.15%, respectively. In summary, electrochemical cell lysis has a good prospect for sludge reduction.

PSIII-23 Effect of feed antioxidants on behavior and stress resistance of fattening pigs

Antioxidants application (selenium, vitamin E and flavonoids) in pig diets provides solving the problem of oxidative stress effects. The research aims to study the efficiency of supplement Taxifolin feeding to reduce the stress effects. Experiments were performed using crossbred [(BWxL)xD] pigs (BW1=34.5–34.9 kg, N=36, n = 9) during the fattening period. Animals were allocated to 4 groups: 1 – control (standard forage – SF, without stress – STR-), 2 – control (SF, STR+), 3 – experimental (SF+0.2 mg kg Se, STR+), 4 – experimental group (SF+32 mg kg TAX, STR+). The animals were kept for 3 heads in a stall and to simulate technological stress, they were rotated within the 2nd, 3rd, and 4th groups every 14 days. The incidence of animal anxiety was directly dependent on the recorded acts of aggression (17%; 29%; 29%; 25% & 8%; 27%; 35%; 30% of the total incidence, according to the experimental groups). In general, for the whole fattening period, the average daily gain increase by 1,6% was recorded in the fourth experimental group compared to the first control group (1012.1±43.5 vs. 996.4±32.8 g, P > 0.5). The Taxifolin effect was manifested as an “adaptive factor” to external stimuli under simulated stress, and contributed to a decrease in cortisol level in the animals’ blood at the end of the experiment (215±53 vs. 309±107, 294±111, 305±61 nmol/l, P > 0.5). At the end of the experiment pigs fed with Taxifolin had the higher lysis rate by 19.2% (42.0±4.8 vs. 22.8±2.5, P < 0.5), the lysozyme content in the blood serum – by 0.35 µg/ml (0.79±0.10 vs. 0.44±0.04 µg/ml, P < 0,5) compared to the control. Consequently, stressors prevention by using natural antioxidants (bioflavonoids) is justified. The work was supported by the grant No. 19-16-00068 of the Russian Science Foundation and GZ АААА-А18-118021590136-7.

Fibrinolysis of Contracted Blood Clots Depends on Whether Plasminogen Activator Acts from inside or Outside

Fibrinolysis involves the dissolution of polymeric fibrin networks that is required to restore blood flow through vessels obstructed by clots and thrombi. The efficiency of lysis depends on the susceptibility of fibrin to enzymatic digestion, which is governed by the structure and spatial organization of fibrin fibers as well as porosity and composition of the clot. Platelet-driven clot contraction results in compaction of the erythrocytes into the core of the clot, effectively reducing the permeability of the clot, and influences fibrin network structure. We have shown that clot contraction is reduced in blood from patients with thrombotic conditions such ischemic stroke and deep vein thrombosis, which points to the clinical importance of understanding the influence of clot contraction on efficacy of fibrinolysis. Here, we examined the effects of clot contraction on the rate of internal fibrinolysis emanating from within the clot to simulate (patho)physiological conditions, and external fibrinolysis initiated from the clot exterior to simulate therapeutic thrombolysis. Fibrinolysis was induced and the kinetics of lysis was measured in parallel in contracted versus uncontracted clots from the same citrated human blood samples. Clot formation and platelet activation were initiated with 1 U/ml thrombin and 2 mM CaCl2. Clot contraction was either unaffected or impaired by inhibiting platelet non-muscle myosin IIa (blebbistatin), actin polymerization (latrunculin A), and platelet-fibin(ogen) binding (abciximab). To examine internal fibrinolysis, 75 ng/ml of human recombinant tissue plasminogen activator (tPA) was added prior to initiation of clotting, allowing for tPA to be uniformly distributed through the clot volume and for fibrinolysis occur after the clot has formed. We used optical tracking to follow clot size in a time dependent manner. Contracted clots were completely lysed at a rate that was at least 2 times faster than clots with impaired contraction. Specifically, the average time to complete lysis was 33±4 minutes for contracted clots versus 59±3, 84±4, 75±3 minutes when contraction was impaired by blebbistatin, latrunculin A, and abciximab, respectively (p<0.001). To examine external fibrinolysis, blood spiked with purified human 125I-fibrinogen was allowed to clot and contract (unless contraction was inhibited) prior to the addition of 75 ng/ml tPA. Clots with impaired contraction released 2-4-fold more radiolabeled soluble degradation products during the first 30 minutes and continued to lyse at a rate 4-fold faster than contracted clots over the initial 4 hours following addition of tPA. This reduction of the fibrinolysis rate in contracted clots was not due to the expulsion of serum-soluble anti-fibrinolytic compounds during the contraction process because serum replacement with a buffer did not affect the lysis rate. This difference in the susceptibility of contracted and uncontracted clots to internal versus external lysis suggests that the lysis rate is dominated by the interplay of clot permeability to fibrinolytic enzymes and the spatial proximity of the fibrin fibers themselves. Despite limitations of in vitro experimental models, numerous studies on fibrinolysis have demonstrated the relevance of experimental findings to pathophysiological fibrinolysis and therapeutic thrombolysis. Enhancement of fibrinolysis in contracted blood clots is consistent with the need to dissolve mature clots once they have performed their hemostatic function in a vessel on in a wound. The reduced rates of dissolution of contracted clots in our model of externally applied tPA could account for the inefficacy of therapeutic thrombolysis of old thrombi that likely underwent more compaction compared to newer thrombi. Our studies point to the clinical importance of understanding how mechanical remodeling of clots and thrombi may influence their fibrinolytic resolution and could inform the development of improved thrombolytic therapies. This work, in part, was supported by the Program for Competitive Growth at KFU. Disclosures No relevant conflicts of interest to declare.

Robust, linear correlations between growth rates and β-lactam–mediated lysis rates

It is widely acknowledged that faster-growing bacteria are killed faster by β-lactam antibiotics. This notion serves as the foundation for the concept of bacterial persistence: dormant bacterial cells that do not grow are phenotypically tolerant against β-lactam treatment. Such correlation has often been invoked in the mathematical modeling of bacterial responses to antibiotics. Due to the lack of thorough quantification, however, it is unclear whether and to what extent the bacterial growth rate can predict the lysis rate upon β-lactam treatment under diverse conditions. Enabled by experimental automation, here we measured >1,000 growth/killing curves for eight combinations of antibiotics and bacterial species and strains, including clinical isolates of bacterial pathogens. We found that the lysis rate of a bacterial population linearly depends on the instantaneous growth rate of the population, regardless of how the latter is modulated. We further demonstrate that this predictive power at the population level can be explained by accounting for bacterial responses to the antibiotic treatment by single cells. This linear dependence of the lysis rate on the growth rate represents a dynamic signature associated with each bacterium–antibiotic pair and serves as the quantitative foundation for designing combination antibiotic therapy and predicting the population-structure change in a population with mixed phenotypes.

The effect of strain level diversity on robust inference of virus-induced mortality

Infection and lysis of phytoplankton by viruses affects population dynamics and nutrient cycles within oceanic microbial communities. However, estimating the quantitative rates of viral-induced lysis remains challenging in situ. The modified dilution method is the most commonly utilised empirical approach to estimate virus-induced killing rates of phytoplankton. The lysis rate estimates of the modified dilution method are based on models of virus-host interactions involving only a single virus and a single host population. Here, using modelling approaches, we examine the robustness of the modified dilution method in multi-strain, complex communities. We assume that strains differ in their life history traits, including growth rates (of hosts) and lysis rates (by viruses). We show that trait differences affect resulting experimental dynamics such that lysis rates measured using the modified dilution method may be driven by the fastest replicating strains; which are not necessarily the most abundant in situ. We discuss the implications of using the modified dilution method and alternative dilution-based approaches for estimating viral-induced lysis rates in marine microbial communities.

Optimization of liquid media and biosafety assessment for algae-lysing bacterium NP23

To control algal bloom caused by nutrient pollution, a wild-type algae-lysing bacterium was isolated from the Baiguishan reservoir in Henan province of China and identified as Enterobacter sp. strain NP23. Algal culture medium was optimized by applying a Placket–Burman design to obtain a high cell concentration of NP23. Three minerals (i.e., 0.6% KNO3, 0.001% MnSO4·H2O, and 0.3% K2HPO4) were found to be independent factors critical for obtaining the highest cell concentration of 1013 CFU/mL, which was 104 times that of the control. In the algae-lysing experiment, the strain exhibited a high lysis rate for the 4 algae test species, namely, Chlorella vulgari, Scenedesmus, Microcystis wesenbergii, and Chlorella pyrenoidosa. Acute toxicity and mutagenicity tests showed that the bacterium NP23 had no toxic and mutagenic effects on fish, even in large doses such as 107 or 109 CFU/mL. Thus, Enterobacter sp. strain NP23 has strong potential application in the microbial algae-lysing project.

Optimized culture condition for enhancing lytic performance of waste activated sludge by Geobacillus sp. G1

Hydrolysis is known as the rate-limiting step during waste activated sludge (WAS) digestion. The optimization of the culture conditions of Geobacillus sp. G1 for enhancing WAS hydrolysis was conducted in this study with uniform design and response surface methodology. Taking the lysis rate of Escherichia coli as the response, the Plackett–Burman design was used to screen the most important variables. Experimental results showed that the maximum predicted lysis rate of E. coli was 50.9% for 4 h treatment time with concentrations of skim milk, NaCl and NH4SO4 at 10.78, 4.36 and 11.28 g/L, respectively. The optimized dosage ratio of Geobacillus sp. G1 to WAS was 35%:65% (VG1:VWAS). Under this condition, soluble protein was increased to 695 mg chemical oxygen demand (COD)/L, which was 5.0 times higher than that obtained in the control (140 mg COD/L). The corresponding protease activity reached 1.1 Eu/mL. Scanning electron microscopy showed that abundant cells were apparently lysed with treatment of Geobacillus sp. G1.

A novel natural mutation AαPhe98Ile in the fibrinogen coiled-coil affects fibrinogen function

SummaryThe aim of this study was to investigate the structure and function of fibrinogen obtained from a patient with normal coagulation times and idiopathic thrombophilia. This was done by SDS-PAGE and DNA sequence analyses, scanning electron microscopy, fibrinopeptide release, fibrin polymerisation initiated by thrombin and reptilase, fibrinolysis, and platelet aggregometry. A novel heterozygous point mutation in the fibrinogen Aα chain, Phe98 to Ile, was found and designated as fibrinogen Vizovice. The mutation, which is located in the RGDF sequence (Aα 95–98) of the fibrinogen coiled-coil region, significantly affected fibrin clot morphology. Namely, the clot formed by fibrinogen Vizovice contained thinner and curled fibrin fibers with reduced length. Lysis of the clots prepared from Vizovice plasma and isolated fibrinogen were found to be impaired. The lysis rate of Vizovice clots was almost four times slower than the lysis rate of control clots. In the presence of platelets agonists the mutant fibrinogen caused increased platelet aggregation. The data obtained show that natural mutation of Phe98 to Ile in the fibrinogen Aα chain influences lateral aggregation of fibrin protofibrils, fibrinolysis, and platelet aggregation. They also suggest that delayed fibrinolysis, together with the abnormal fibrin network morphology and increased platelet aggregation, may be the direct cause of thrombotic complications in the patient associated with pregnancy loss.