Microbial Surface Research Articles

Physicochemical and antigenic properties of the urea-extracted surface structures of <i>Yersinia pseudotuberculosis</i> O:1b

Immuno-serological diagnostic tools particularly identifying pathogen antigens are the most important methods of pseudotuberculosis studies. The main immunodominant and species-specific antigens located in the surface structures of the bacterial cell are of practical interest. Thereby the aim of the work was to isolate and characterize biologically active surface structures of the pseudotuberculosis microbe. Here, the living cells of Y. pseudotuberculosis 3704 (O:1b) were lysed by using 9 M urea solution to extract antigens localized in the microbial surface structures. The subcellular fractions obtained such as outer membranes (OM), urea extract (UE) and isolated protein-lipopolysaccharide complex (PLPSC) are characterized by physical and chemical parameters. The protein content in the preparations ranged from 42% to 53%. The polypeptide band of the OM preparation, UE polypeptide and PLPSC for pseudotuberculosis microbe was presented by 14, 16 and 9 major polypeptides with molecular weight ranging from 13.9 kDa to 131.5 kDa, 13.5 kDa to 101.6 kDa, and 20.7 kDa to 66.6 kDa, respectively. Proteolytically active proteins and polypeptides were detected in isolated subcellular fractions (OM and UE) by using the radial enzyme diffusion test and substrate-gel electrophoresis found to be presented by 4 and 7 polypeptides with molecular weight ranging from 28.0 kDa to 118.0 kDa and 29.2 kDa to 97.7 kDa in the OM and UE preparation, respectively. The subcellular fractions obtained are capable to exhibit immunogenic activity after inoculation to experimental animals and antigenic activity while interacting with specific antibodies in the radial immunodiffusion (RID) assay and antibodies labeled with colloidal silver nanoparticles in dot immunoassay (DIA). OM and PLPSC preparations in DIA with immunoglobulins isolated from experimental antisera and labeled with colloidal silver nanoparticles were detected at a concentration of 0.12 g/ml (dry weight), cells of strain Y. pseudotuberculosis 3704 at a concentration of 3, 9 106 m.c./ml, which is similar to the results of DIA with immunoglobulins isolated from commercial pseudotuberculosis antiserum (St. Petersburg) and labeled with nanoparticles of colloidal silver. Thus, the subcellular fractions of pseudotuberculosis microbe isolated by using urea as a lysing and decontaminating agent retain their antigenic and immunogenic properties and enzymatic activity suggesting about their potential benefits for use to improve early diagnostics of pseudotuberculosis.

Role of Salmonella Newport cell surface structures on bacterial attachment and transfer during cucumber peeling.

Fresh cucumbers have been recognized as a vehicle in foodborne disease outbreaks since several multistate outbreaks of salmonellosis linked to fresh cucumbers occurred in the United States. Little is known about how microbial cell surface characteristics that are known to affect adhesion can influence bacterial cross-contamination and transfer. This study investigated the role of S. Newport cell surface components on bacterial attachment and transfer in cucumbers. Wild type Salmonella Newport and its transposon mutants were used to inoculate cucumbers. Attachment strength of S. Newport wild type to cucumber was not significantly different than that of mutants. Log10 percent transfer of mutant strains to edible flesh was not different from the wild type. Significantly less wild type Salmonella remained on the peel and transferred to the peeler than one mutant did, but not the other. Our results suggest that while curli and cellulose enhance Salmonella attachment to surface of cucumbers, there appear to be other mechanisms and factors that govern Salmonella transfer in cucumbers.

Genomic analysis of the progenitor strains of Staphylococcus aureus RN6390.

RN6390 is a commonly used laboratory strain of Staphylococcus aureus derived from NCTC8325. In this study, we sequenced the RN6390 genome and compared it to available genome sequences for NCTC8325. We confirmed that three prophages, Φ11, Φ12 and Φ13, which are present in NCTC8325 are absent from the genome of RN6390, consistent with the successive curing events leading to the generation of this strain. However, we noted that a separate prophage is present in RN6390 that is not found in NCTC8325. Two separate genome sequences have been deposited for the parental strain, NCTC8325. Analysis revealed several differences between these sequences, in particular, between the copy number of esaG genes, which encode immunity proteins to the type VII secreted anti-bacterial toxin, EsaD. Single nucleotide polymorphisms were also detected in ribosomal RNA genes and genes encoding microbial surface components recognizing adhesive matrix molecules (MSCRAMM) between the two NCTC8325 sequences. Comparing each NCTC8325 sequence to other strains in the RN6390 lineage confirmed that sequence assembly errors in the earlier NCTC8325 sequence are the most likely explanation for most of the differences observed.

Staphylococcus epidermidis Pathogenesis: Interplay of icaADBC Operon and MSCRAMMs in Biofilm Formation of Isolates from Pediatric Bacteremia in Peshawar, Pakistan.

Background and Objective: Staphylococcus epidermidis is an opportunistic pathogen from pediatric bacteremia that is commonly isolated. Biofilm is the major virulence factor of S. epidermidis; however, the role of biofilm determinants in biofilm formation is highly contradictory and diverse. The current study aimed to investigate the role of polysaccharide-dependent and polysaccharide-independent pathogenic determinants in biofilm formation under physiological stress conditions. Materials and Methods: The isolates (n = 75) were identified and screened for the icaADBC operon, IS256, and an array of MSCRAMMs (Microbial Surface Component Recognizing Adhesive Matrix Molecules) through PCR analysis. The activity of the icaADBC operon was detected by Congo red assay, and the biofilm formation was analyzed through microtiter plate assay. Results: S. epidermidis isolates produced biofilm (n = 65; 86.6%) frequently. The icaA was the major representative module of the actively expressing icaADBC operon (n = 21; 80.7% sensitivity). The MSCRAMMs, including fbe (n = 59; 90.7%; p = 0.007), and embp (n = 57; 87.6%; p = 0.026), were highly prevalent and associated with biofilm positive S. epidermidis. The prevalence of icaADBC operon in biofilm positive and negative S. epidermidis was not significant (n = 41; 63%; p = 0.429). No significant association was found between IS256 and actively complete icaADBC operon (n = 10; 47.6%; p = 0.294). In the presence of 5% human plasma and glucose stress, S. epidermidis produced a strong biofilm (n = 55; 84.6%). Conclusion: The polysaccharide-dependent biofilm formation is significantly replaced (n = 21; 28%; p = 0.149) by a polysaccharide-independent mechanism (n = 59; 90.7%; p = 0.007), in which the MSCRAMMs might actively play their role. The fibrinogen-binding protein and extracellular matrix-binding protein might be potential anti-biofilm drug targets, markers of rapid diagnosis, and potential vaccine candidates of S. epidermidis involved in pediatric bacteremia.

Death at the interface: Nanotechnology's challenging frontier against microbial surface colonization.

The emergence of antimicrobial-resistant bacterial strains has led to novel approaches for combating bacterial infections and surface contamination. More specifically, efforts in combining nanotechnology and biomimetics have led to the development of next-generation antimicrobial/antifouling nanomaterials. While nature-inspired nanoscale topographies are known for minimizing bacterial attachment through surface energy and physicochemical features, few studies have investigated the combined inhibitory effects of such features in combination with chemical alterations of these surfaces. Studies describing surface alterations, such as quaternary ammonium compounds (QACs), have also gained attention due to their broad spectrum of inhibitory activity against bacterial cells. Similarly, antimicrobial peptides (AMPs) have exhibited their capacity to reduce bacterial viability. To maximize the functionality of modified surfaces, the integration of patterned surfaces and functionalized exteriors, achieved through physical and chemical surface alterations, have recently been explored as viable alternatives. Nonetheless, these modifications are prone to challenges that can reduce their efficacy considerably in the long term. Their effectiveness against a wider array of microbial cells is still a subject of investigation. This review article will explore and discuss the emerging trends in biomimetics and other antimicrobials while raising possible concerns about their limitations and discussing future implications regarding their potential combined applications.

Adhesive Virulence Factors of Staphylococcus aureus Resist Digestion by Coagulation Proteases Thrombin and Plasmin.

Staphylococcus aureus (S. aureus) is an invasive and life-threatening pathogen that has undergone extensive coevolution with its mammalian hosts. Its molecular adaptations include elaborate mechanisms for immune escape and hijacking of the coagulation and fibrinolytic pathways. These capabilities are enacted by virulence factors including microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) and the plasminogen-activating enzyme staphylokinase (SAK). Despite the ability of S. aureus to modulate coagulation, until now the sensitivity of S. aureus virulence factors to digestion by proteases of the coagulation system was unknown. Here, we used protein engineering, biophysical assays, and mass spectrometry to study the susceptibility of S. aureus MSCRAMMs to proteolytic digestion by human thrombin, plasmin, and plasmin/SAK complexes. We found that MSCRAMMs were highly resistant to proteolysis, and that SAK binding to plasmin enhanced this resistance. We mapped thrombin, plasmin, and plasmin/SAK cleavage sites of nine MSCRAMMs and performed biophysical, bioinformatic, and stability analysis to understand structural and sequence features common to protease-susceptible sites. Overall, our study offers comprehensive digestion patterns of S. aureus MSCRAMMs by thrombin, plasmin, and plasmin/SAK complexes and paves the way for new studies into this resistance and virulence mechanism.

Antimicrobial activity of major royal jelly protein 8 and 9 of honeybee (Apis mellifera) venom

• Apis mellifera has major royal jelly protein 8 and 9 (AmMRJP 8 and 9) in its venom. • AmMRJP 8 and 9 inhibit microbial serine proteases. • AmMRJP 8 and 9 exhibit antibacterial and antifungal activities. • AmMRJP 8 and 9 act as antimicrobial agents in honeybee venom. Honeybee venom is a complex mixture of toxic components, including major royal jelly protein (MRJP) 8 and 9. MRJP 8 and MRJP 9 are allergens, and MRJP 8 reduces melittin-induced cell apoptosis. However, their functional roles are poorly understood, and their antimicrobial activities have not been determined. In this study, the antimicrobial role of MRJP 8 and MRJP 9 of honeybee ( Apis mellifera ) venom (AmMRJP 8 and AmMRJP 9) was demonstrated. The presence of AmMRJP 8 and AmMRJP 9 in the secreted venom was observed using antibodies against recombinant AmMRJP 8 and AmMRJP 9 produced in baculovirus-infected insect cells. Recombinant AmMRJP 8 and AmMRJP 9 exhibited an inhibitory activity against microbial serine proteases. Consistent with their inhibitory activity, they induced structural damage by binding to microbial surfaces, resulting in a broad-spectrum antimicrobial activity against bacteria and fungi. They had little effect on hemolysis. Therefore, AmMRJP 8 and AmMRJP 9 could function as antimicrobial agents in honeybee venom.

Positive biofilms to control surface-associated microbial communities in a broiler chicken production system - a field study.

In the One Health concept, the use of beneficial bacteria to form positive biofilms that prevent the settlement of undesirable bacteria is a promising solution to limit the use of antimicrobials on farms. However, there is a lack of field studies reporting the onset of these beneficial bacteria after application and the effects on autochthonous surface microbiota. In the study reported here, the inner surfaces of commercial broiler chicken houses were treated or not with a bacterial consortium composed of Bacillus spp. and Pediococcus spp. strains, able to form covering biofilms in different laboratory models. Preinstalled coupons were sampled over time to capture microbial biofilm dynamics on-farm surfaces. The results showed that the bacterial consortium can establish on the farm surfaces, modulate microbial communities, and limit the implantation of Enterobacteriaceae and Enterococcaceae, two families containing potential pathogens.

Prevention of Initial Bacterial Attachment by Osteopontin and Other Bioactive Milk Proteins.

A considerable body of work has studied the involvement of osteopontin (OPN) in human physiology and pathology, but comparably little is known about the interaction of OPN with prokaryotic cells. Recently, bovine milk OPN has been proposed as a therapeutic agent to prevent the build-up of dental biofilms, which are responsible for the development of caries lesions. Bioactive milk proteins are among the most exciting resources for caries control, as they hamper bacterial attachment to teeth without affecting microbial homeostasis in the mouth. The present work investigated the ability of OPN to prevent the adhesion of three dental biofilm-forming bacteria to saliva-coated surfaces under shear-controlled flow conditions in comparison with the major milk proteins α-lactalbumin, β-lactoglobulin, αs1-casein, β-casein and κ-casein, as well as crude milk protein. OPN was the most effective single protein to reduce the adhesion of Actinomyces naeslundii, Lactobacillus paracasei subsp. paracasei and Streptococcus mitis. β-casein and crude milk protein also had a pronounced effect on all three species, which suggests binding to different microbial surface structures rather than the blocking of a specific bacterial adhesin. Bioactive milk proteins show potential to delay harmful biofilm formation on teeth and hence the onset of biofilm-related oral disease.

Cationic protein 8 plays multiple roles in Galleria mellonella immunity

Galleria mellonella cationic protein 8 (GmCP8) is a hemolymph protein previously identified as an opsonin and an inhibitor of fungal proteases. In this work, we showed its bactericidal activity toward Pseudomonas entomophila, Pseudomonas aeruginosa, Bacillus thuringiensis, Staphylococcus aureus, and Escherichia coli and against yeast-like fungi Candida albicans. The activity against E. coli was correlated with bacterial membrane permeabilization. In turn, in the case of P. entomophila, B. thuringiensis, and C. albicans, the atomic force microscopy analysis of the microbial surface showed changes in the topography of cells and changes in their nanomechanical properties. GmCP8 also showed the inhibitory activity toward the serine protease trypsin and the metalloproteinase thermolysin. The expression of the gene encoding the GmCP8 protein did not increase either in the gut or in the fat body of G. mellonella after oral infection with P. entomophila. Similarly, the amount of GmCP8 in the hemolymph of G. mellonella did not change in immune-challenged insects. However, when GmCP8 was injected into the G. mellonella hemocel, a change in the survival curve was observed in the infected larvae. Our results shed new light on the function of GmCP8 protein in insect immunity, indicating its role in humoral defence mechanisms.

A New Crustin Gene Homolog SpCrus8 Identified in Scylla paramamosain Exerting In Vivo Protection Through Opsonization and Immunomodulation.

Crustins are the most abundant class of antimicrobial peptides in crustaceans and are essential for protecting animals from infection. Among them, type II crustins usually exhibit potent antimicrobial activity. Interestingly, in this study, a newly identified type II crustin gene homolog (named SpCrus8) from mud crab Scylla paramamosain, the recombinant proteins of which (rSpCrus8 and rTrx-SpCrus8) showed no obvious antibacterial effects, but could significantly reduce the bacterial load in crab hemolymph and improve the survival rate of crabs infected with Vibrio alginolyticus. The immune-related function of SpCrus8 and the underlying mechanism deserve further investigation. It was found that the SpCrus8 gene was widely distributed in various tissues of adult crabs. In the hepatopancreas of crabs infected with V. alginolyticus or Staphylococcus aureus, transcripts of the SpCrus8 gene were remarkably induced, indicating that the SpCrus8 gene was involved in the immune response to bacterial infection in vivo. In addition, rSpCrus8 and rTrx-SpCrus8 had strong binding activity not only to microbial surface components (lipopolysaccharide, lipoteichoic acid, peptidoglycan, and glucan), but also to the tested bacteria (S. aureus, Pseudomonas aeruginosa and V. alginolyticus). Notably, rSpCrus8 and rTrx-SpCrus8 could significantly promote hemocyte phagocytosis. After rSpCrus8 and rTrx-SpCrus8 treatment, a large number of fluorescent microspheres were observed to aggregate into clusters and be phagocytosed by multiple hemocytes, while hemocytes in the control group phagocytosed only individual microspheres, indicating that SpCrus8 played an important role in opsonization. When the SpCrus8 gene was knocked down, the expression levels of the key phagocytosis-related genes SpRab5 and SpRab7 were significantly downregulated, as well as the IMD signaling pathway genes SpIKKβ and SpRelish, and another crustin gene SpCrus5. Correspondingly, all the SpIKKβ, SpRelish and SpCrus5 genes were significantly upregulated after rSpCrus8 treatment, suggesting that SpCrus8 might be involved in the immunomodulation of S. paramamosain. Taken together, this study revealed the immune-related functions of the SpCrus8 gene in opsonization and regulation, which will help us further understand the role of the crustin gene family in the immune system of mud crabs and provide new insights into the function of type II crutins.

Dual function of a bumblebee (Bombus ignitus) serine protease inhibitor that acts as a microbicidal peptide and anti-fibrinolytic venom toxin

In bee venoms, low–molecular-weight peptides, including serine protease inhibitors (SPIs), exhibit multifunctional activities. Although SPIs in bee venoms are relatively well known, those that function in both the body and secreted venom of bees are not well-characterized. In this study, we identified a bumblebee (Bombus ignitus) SPI (BiSPI) that displays microbicidal and anti-fibrinolytic activities. BiSPI was found to consist of a trypsin inhibitor–like domain containing a P1 site and ten cysteine residues. We observed that the BiSPI gene was ubiquitously transcribed in the body, including the venom glands. In correlation, the BiSPI protein was detected both in the body and secreted venom by using an antibody against a recombinant BiSPI peptide produced in baculovirus-infected insect cells. Recombinant BiSPI exhibited inhibitory activity against trypsin but not chymotrypsin and inhibited microbial serine proteases and plasmin but not elastase or thrombin. Moreover, recombinant BiSPI recognized carbohydrates and bound to fungi and gram-negative and gram-positive bacteria. Consistent with these properties, recombinant BiSPI exhibited microbicidal activities against bacteria and fungi through induction of structural damage by binding to the microbial surfaces. Additionally, recombinant BiSPI inhibited the plasmin-mediated degradation of human fibrin and was thus concluded to exhibit anti-fibrinolytic activity. Moreover, the peptide showed no effect on hemolysis. These findings demonstrate the dual function of BiSPI, which acts as a microbicidal peptide and anti-fibrinolytic venom toxin.

Microbial Growth and Calcium Carbonate Nucleation Properties in Mineral Admixtures

In this study, steel slag powder and fly ash were used as reinforcement and modification materials, and their effects on the growth, survival, and nucleation of mineral admixtures on bacteria were analyzed. Electrical conductivity, urease activity, and zeta potential tests were conducted, and the results showed that: (1) different mineral environments had different effects on the urease activity of Sporosarcina pasteurii. The steel slag powder solution inhibited urease activity, while the fly ash solution promoted urease activity. (2) S. pasteurii showed different growth characteristics in different mineral environments, especially in the fly ash solution, which showed higher hydrolysis efficiency, urease activity, and calcium carbonate yield. (3) The zeta potential test results showed that the nucleation of mineral admixtures on bacteria started to occur when the calcium ion concentration in the mineral filtrate was higher than 15 mmol/L. Different calcium ion concentrations showed greater impacts on the nucleation rate of mineral admixtures. The results of this study indicated the adaptability of microorganisms in the steel slag powder and fly ash solutions and the nucleation characteristics of calcium carbonate on the microbial surface, providing a theoretical and experimental basis for the subsequent development of new sand-fixing materials.

Ecotoxicological Evaluatation of Artisanal Effluents on Bacillus, Enterobacter, Amorphotheca, Cladosporium and Penicillium Species in Brackish Water

Aim: To assess the effect of the hydrocarbon discharges from the artisanal refineries on the community structure of microbial mats in an aquatic environment
 Study Design: The study employs experimental design, statistical analysis of the data and interpretation.
 Place and Duration of Study: The microbial mats, surface water and sediments samples were collected from four hydrocarbon polluted stations (A, B, C and D) and a control sampling station in Yellow island (Iyalla kiri) in Degema Local Government Area, in Rivers state Nigeria. The samples were immediately transported with ice packs to the Microbiology Laboratory of Rivers State University, Port Harcourt. The study lasted from March 2020 to February 2021, covering both wet and dry seasons.
 Methodology: Different concentrations of fresh effluent (0, 1.625, 3.25, 6.5, 12.5, 25, 50 and 75%) were prepared in test tubes to final volume of 10ml. Each of the test tubes was inoculated with one milliliter (1ml) of the test organism. Five sets of concentrations were prepared for the five test organisms (Bacillus subtillis MW808817, Enterobacter ludwigiiMW767009, Amorphotheca resinae EU040230, Cladosporium cladosporioides MW793722 and Penicillium chrysogenum MN184857). The organisms were exposed to the pollutant for duration of 0, 4, 8, 12 and 24 hours and plated out using spread plate technique. The cultures were incubated for 24 hours for bacteria and five days for fungi. Median lethal concentration (LC50) was determined using SPSS version 20.
 Results: The results showed that the percentage logarithm survival of the test organisms decreased with increase in exposure time and concentration. The LC50 of Bacillus subtillis MW808817 was 30.93%, Enterobacter ludwigii MW767009 was 29.74%, Amorphotheca resinae EU040230 was 19.65%,Cladosporium cladosporioides MW793722 was 20.08% and Penicillium chrysogenum MN184857 was 17.77%, (noting; the lower the LC50 the more toxic the pollutant).
 Conclusion: The effluent discharge was more toxic on Penicillium chrysogenum MN184857 than the other test organisms. Also, the ecotoxicological evaluation of the effluents on the test organisms isolated from the study area showed that LC50 of the effluent was slightly toxic on the microbial population when the results obtained were compared to GESAMP Standard for Toxicity Ranking of Chemicals/Effluents in Marine Environment.

Removal mechanisms of aqueous Cr(VI) by anaerobic fermentation sludge

ABSTRACT After fermentation, activated sludge contains many acid-producing bacteria and their metabolites, which have a good reducing effect. Various active groups (e.g., hydroxyl, amino, carboxyl, and phosphate) on microbial cell surfaces can adsorb heavy metals through complexation or chelation, forming heavy metal precipitates and thereby reducing the toxicity of heavy metals. However, the effects and mechanisms of using sludge after anaerobic fermentation to remove Cr(VI) are unclear, such as the dominance of direct versus indirect biological reduction, the contribution of abiotic effects, and the influence of fermentation conditions. This paper compares Cr(VI) removal in fermented and unfermented sludges. After fermentation for 24 h, 99.9% of the Cr(VI) (50 mg/L) in anaerobic sludge was removed within 7 h, which was twice the rate in unfermented activated sludge. A series of comparative experiments demonstrated that Cr(VI) removal primarily occurred through biological effects (about 92%), which included biological reduction and biosorption. 16SrRNA gene sequencing revealed that Cr(VI) transformation primarily occurred through direct biological reduction, with the related genera being Trichococcus, Acetobacter, Aeromonas, and Tolumonas. Fourier-transform infrared (FTIR) spectroscopy results showed that the C = O and C–O functionalities on sludge were likely involved in the Cr(VI) conversion. Majority of the Cr(VI) in the system was reduced to Cr(III) and existed in the suspension, with a small amount deposited on the sludge surface. The X-ray photoelectron spectroscopy (XPS) results indicated that the majority of Cr was present as reduced Cr(III) on the sludge. These results demonstrate that after fermentation in an aqueous environment, activated sludge is an effective medium for the remediation of Cr(VI). These results are useful for designing a green and sustainable bioreduction system for the remediation of Cr(VI)-polluted water.

Density of Compatible Ligands on the Surface of Food Particles Modulates Sorting Efficiency in the Blue Mussel Mytilus edulis

The adhesion between food particles and mucus is a fundamental process in particle sorting in suspension-feeding bivalves that requires specific recognition. Interactions between carbohydrate-binding proteins (lectins) expressed on the feeding organs and carbohydrates present on microbial cell surface can provide this specificity. Microalga cell surface carbohydrates (MCSC) represent unique patterns that can be considered as species-specific fingerprints. In this study, sorting efficiencies in blue mussels Mytilus edulis fed with microalgae having modified MCSC and engineered microspheres coated with target carbohydrates was measured. The nature and quantities of surface carbohydrates required to trigger sorting in mussels was evaluated and the relationship between ligand quantities and sorting efficiency (SE) was determined. Mussels fed with Chlamydomonas which MCSC were blocked with ConA or PEA lectins (affinity to mannose and glucose) led to a significant decrease of the sorting efficiencies, not observed when the lectin UEA (affinity to fucose) was used. The ability of commercial lectins to inhibit sorting was not linear and a threshold was noted between 30 and 45 ug lectins per million algae cells. Further, mussels were fed with microspheres coated with neoglycoproteins. Results showed that glucose-BSA, but not fucose-BSA, has an effect on particle sorting in mussels, and 1.08 x 109 molecules of glucose per microspheres, corresponding to a density of 6.99 x 106 molecules of glucose per µm2, triggers particle selection. These findings support that selection of food particles by mussels rely on the strength of the bond between suspended particle and the mucosal layer that mediate sorting, and that these bonds depend on the quantity of compatible ligands on each particle.

Drying and rewetting induce changes in biofilm characteristics and the subsequent release of metal ions

Drying and rewetting can markedly influence the microbial structure and function of river biofilm communities and potentially result in the release of metal ions from biofilms containing metals. However, little information is available on the response of metal-enriched biofilms to drying and rewetting over time. In this study, natural biofilms were allowed to develop in four rotating annular bioreactors for 2–11 weeks, followed by drying for 5 days and rewetting for another 5 days. Subsequently, we assessed Zn, Cd, and As desorption from the biofilms and other related parameters (microbial community structure, biofilm morphology, enzyme activity, and surface components as well as characteristics). High-throughput sequencing of the 16 S rRNA gene and confocal laser scanning microscopy revealed that the biofilm architecture and bacterial communities were distinct in different growth phases and under drying and rewetting conditions (permutational multivariate analysis of variance; p = 0.001). Proteobacteria was the dominant bacterial phylum, accounting for 69.7–90.1% of the total content. Kinetic experiments revealed that the drying and rewetting process increased metal desorption from the biofilm matrix. The desorption of heavy metals was affected by the age of the biofilm, with the maximum amount of metal ions released from 2-week-old biofilms (one-way ANOVA, Zn: p < 0.001; Cd: p = 0.008; As: p < 0.001). The modifications in biofilm properties and decreased diversity of the bacterial community (paired t-test, p < 0.05) after drying and rewetting decreased the number of specific binding sites for metal ions. In addition, negatively charged arsenate and other anions in the liquid phase could compete with As ions for adsorption sites to promote the release of As(V) and/or reductive desorption of As(III). The results of this study and their interpretation are expected to help refine the behaviors of heavy metals in the aquatic environment.

Investigating the Effect of Selected Ultraviolet Light Emitting Diode Treatments on the Inactivation of B. subtilis, the Pasting Properties and the Surface Morphology of Tapioca Starch

AbstractThis study investigates various ultraviolet light emitting diode (UV LED) treatments on the microbial load, pasting profile, and surface morphology of tapioca starch. Tapioca starch samples are subjected to various UV LED treatments employing different wavelengths (280, 300, and 365 nm) and treatment durations (5, 10, and 20 min). For microbiological analysis tapioca starch samples are inoculated with Bacillus subtilis and subjected to treatment. Furthermore, food quality parameters are also investigated by assessing the impact of all UV LED treatments on the pasting profile using rapid visco analysis and the surface morphology using scanning electron microscopy. Significant reductions are achieved for UV LED treatments after 20 min with 300 and 365 nm showing reductions to 4.03 ± 1.55 log10 and 6.52 ± 0.31 log10 cfu g–1, respectively, from 7.53 ± 0.11 log10 cfu g–1. For food quality assessments, no significant changes in pasting properties or surface morphology are observed for any treatment investigated. This study highlights the potential of this technology as a decontamination tool in the food industry.

In Silico Designed Gain-of-Function Variants of Complement C2 Support Cytocidal Activity of Anticancer Monoclonal Antibodies.

Simple SummaryThe complement system can be exploited by anticancer antibody-based therapeutics. Activation of the classical complement pathway by the heavy chain of antibodies eventually leads to the lysis of target cells. However, overexpression of complement inhibitors by tumor cells limits the therapeutic efficacy. We designed and produced recombinant gain-of-function variants of complement C2 protein that counteract the activity of complement inhibitors. The dominant character of designed mutations in C2 allows supplementation of human serum with recombinant proteins for enhancing the cytocidal activity of complement-activating antibodies. In vitro functional assays demonstrate that this strategy is compatible with several clinically approved antibodies.The molecular target for the classical complement pathway (CP) is defined by surface-bound immunoglobulins. Therefore, numerous anticancer monoclonal antibodies (mAbs) exploit the CP as their effector mechanism. Conversely, the alternative complement pathway (AP) is spontaneously induced on the host and microbial surfaces, but complement inhibitors on host cells prevent its downstream processing. Gain-of-function (GoF) mutations in the AP components that oppose physiological regulation directly predispose carriers to autoimmune/inflammatory diseases. Based on the homology between AP and CP components, we modified the CP component C2 so that it emulates the known pathogenic mutations in the AP component, factor B. By using tumor cell lines and patient-derived leukemic cells along with a set of clinically approved immunotherapeutics, we showed that the supplementation of serum with recombinant GoF C2 variants not only enhances the cytocidal effect of type I anti-CD20 mAbs rituximab and ofatumumab, but also lowers the threshold of mAbs necessary for the efficient lysis of tumor cells and efficiently exploits the leftovers of the drug accumulated in patients’ sera after the previous infusion. Moreover, we demonstrate that GoF C2 acts in concert with other therapeutic mAbs, such as type II anti-CD20, anti-CD22, and anti-CD38 specimens, for overcoming cancer cells resistance to complement attack.

Methicillin-Resistant Staphylococcus aureus Hospital-Acquired Pneumonia/Ventilator-Associated Pneumonia.

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). MRSA pneumonia is associated with significant morbidity and mortality. Several virulence factors allow S. aureus to become an effective pathogen. The polysaccharide intracellular adhesin allows for the production of biofilms, some strains can produce capsular polysaccharides that protect against phagocytosis, microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) allow for colonization of epithelial surfaces, and S. aureus secretes several exotoxins that aid in tissue destruction. The α-hemolysin exotoxin secreted by S. aureus is one of the most important virulence factors for the bacteria. The diagnosis of MRSA pneumonia can be challenging; the infection may present as a mild respiratory infection or severe respiratory failure and septic shock. Many individuals are colonized with MRSA and thus a positive nasopharyngeal swab does not confirm infection in the lower respiratory tract. The management of MRSA pneumonia has evolved. Historically, vancomycin has been the primary antibiotic used to treat MRSA pneumonia. Over the past decade, prospective studies have shown that linezolid leads to higher rates of clinical cure. Monoclonal antibodies are being studied as potential therapeutic options. MRSA is an important cause of HAP/VAP; novel diagnostics may facilitate rapid diagnosis of this infection and the available literature should be used to make informed decisions on management.