Biofilms: The Microbial "Protective Clothing" in Extreme Environments

Microbiota manipulation through the secretion of effector proteins is fundamental to the wealth of lifestyles in the fungal kingdom

Fungi are well-known decomposers of organic matter that thrive in virtually any environment on Earth where they encounter wealths of other microbes. Some fungi evolved symbiotic lifestyles, including pathogens and mutualists, that have mostly been studied in binary interactions with their hosts. However, we now appreciate that such interactions are greatly influenced by the ecological context in which they take place. While establishing their symbioses, fungi not only interact with their hosts but also with the host-associated microbiota. Thus, they target the host and its associated microbiota as a single holobiont. Recent studies have shown that fungal pathogens manipulate the host microbiota by means of secreted effector proteins with selective antimicrobial activity to stimulate disease development. In this review, we discuss the ecological contexts in which such effector-mediated microbiota manipulation is relevant for the fungal lifestyle and argue that this is not only relevant for pathogens of plants and animals but also beneficial in virtually any niche where fungi occur. Moreover, we reason that effector-mediated microbiota manipulation likely evolved already in fungal ancestors that encountered microbial competition long before symbiosis with land plants and mammalian animals evolved. Thus, we claim that effector-mediated microbiota manipulation is fundamental to fungal biology.

Role of Biofilm in Bacterial Infection and Antimicrobial Resistance

Biofilm refers to the complex, sessile communities of microbes found either attached to a surface or buried firmly in an extracellular matrix as aggregates. Microbial flora which produces biofilm manifests an altered growth rate and transcribes genes that provide them resistance to antimicrobial and host immune systems. Biofilms protect the invading bacteria against the immune system of the host via impaired activation of phagocytes and the complement system. Biofilm-producing isolates showed greater multidrug resistance than non-biofilm producers. Biofilm causes antibiotic resistance through processes like chromosomally encoded resistant genes, restriction of antibiotics, reduction of growth rate, and host immunity. Biofilm formation is responsible for the development of superbugs like methicillin-resistant Staphylococcus aureus, vancomycin-resistant Staphylococcus aureus, and metallo-beta-lactamase producing Pseudomonas aeruginosa. Regular monitoring of antimicrobial resistance and maintaining hygiene, especially in hospitalized patients are required to control biofilm-related infections in order to prevent antimicrobial resistance.

Recent Advances in the Control of Clinically Important Biofilms

Biofilms are complex structures formed by bacteria, fungi, or even viruses on biotic and abiotic surfaces, and they can be found in almost any part of the human body. The prevalence of biofilm-associated diseases has increased in recent years, mainly because of the frequent use of indwelling medical devices that create opportunities for clinically important bacteria and fungi to form biofilms either on the device or on the neighboring tissues. As a result of their resistance to antibiotics and host immunity factors, biofilms have been associated with the development or persistence of several clinically important diseases. The inability to completely eradicate biofilms drastically increases the burden of disease on both the patient and the healthcare system. Therefore, it is crucial to develop innovative ways to tackle the growth and development of biofilms. This review focuses on dental- and implant-associated biofilm infections, their prevalence in humans, and potential therapeutic intervention strategies, including the recent advances in pharmacology and biomedical engineering. It lists current strategies used to control the formation of clinically important biofilms, including novel antibiotics and their carriers, antiseptics and disinfectants, small molecule anti-biofilm agents, surface treatment strategies, and nanostructure functionalization, as well as multifunctional coatings particularly suitable for providing antibacterial effects to the surface of implants, to treat either dental- or implant-related bacterial infections.

Development and microbial characterization of Bio-RD-PAOP for effective remediation of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) as typical halogenated persistent organic pollutants are widely distributed in natural environments, and can be enriched and magnified in organisms via food webs. It is consequently urgent and necessary to develop techniques to completely remove these persistent organohalides. In this study, we developed a process (Bio-RD-PAOP) by integrating microbial reductive dechlorination (Bio-RD) with subsequent persulfate activation and oxidation process (PAOP) for effective remediation of PCBs. Results showed the synergistic combination of advantages of Bio-RD and PAOP in dechlorination of higher-chlorinated PCBs and of PAOP in degradation/mineralization of lower-chlorinated PCBs, respectively. For the PAOP, both experimental evidences and theoretical calculations suggested that degradation rate and efficiency decreased with the increased PCB chlorine numbers. Relative to the Bio-RD and PAOP, Bio-RD-PAOP had significantly higher PCB removal efficiencies, of which values were PCB congener-specific. For example, removal efficiency of Bio-RD-PAOP in removing PCB88 is 2.50 and 1.86 times of that of Bio-RD and PAOP, respectively. In contrast, the efficiency is 1.66 and 3.35 times of Bio-RD and PAOP, respectively, for PCB180 removal. The PAOP-derived oxidizing species (mainly sulfate free radical) significantly decreased microbial abundance, particularly of the organohalide-respiring Dehalococcoides. Notably, co-existence of other microorganisms alleviated the inhibitive effect of oxidizing species on the Dehalococcoides, possibly due to formation of microbial flocs or biofilm. This study provided a promising strategy for extensive remediation of organohalide-contaminated sites, as well as new insight into impact of PAOP-derived oxidizing species on the organohalide-respiring community.

Alternative Antibiotics in Dentistry: Antimicrobial Peptides

The rise of antibiotic resistant bacteria due to overuse and misuse of antibiotics in medicine and dentistry is a growing concern. New approaches are needed to combat antibiotic resistant (AR) bacterial infections. There are a number of methods available and in development to address AR infections. Dentists conventionally use chemicals such as chlorohexidine and calcium hydroxide to kill oral bacteria, with many groups recently developing more biocompatible antimicrobial peptides (AMPs) for use in the oral cavity. AMPs are promising candidates in the treatment of (oral) infections. Also known as host defense peptides, AMPs have been isolated from animals across all kingdoms of life and play an integral role in the innate immunity of both prokaryotic and eukaryotic organisms by responding to pathogens. Despite progress over the last four decades, there are only a few AMPs approved for clinical use. This review summarizes an Introduction to Oral Microbiome and Oral Infections, Traditional Antibiotics and Alternatives & Antimicrobial Peptides. There is a focus on cationic AMP characteristics and mechanisms of actions, and an overview of animal-derived natural and synthetic AMPs, as well as observed microbial resistance.

Teaming up to make kombucha

Reducing the microbial diversity in a type of fermented tea reveals the core metabolic interactions responsible for the drink’s signature taste and characteristics.

Bacterial-derived extracellular polysaccharides reduce antimicrobial susceptibility on biotic and abiotic surfaces

OBJECTIVE

Extracellular biofilm matrix plays a role in reducing bacterial susceptibility against antimicrobials. Since the surface where biofilm is growing modulates microbial accumulation and bacterial-derived exopolysaccharides (EPS) synthesis, this study compared the role of EPS to reduce antimicrobial susceptibility on biotic (dental surface) and abiotic (titanium (Ti) material) surfaces and the effect of remaining matrix-enriched biofilms to promote bacterial recolonization.

DESIGN

48 h Streptococcus mutans UA159 strain biofilms were grown on enamel and Ti surfaces. The medium was supplemented with 1% sucrose, substrate for EPS synthesis, or with 0.5% glucose + 0.5% fructose as control. Chlorhexidine (CHX) 0.2% was used for antimicrobial treatment. Biofilms were collected and the following analyses were considered: viable bacterial counts, biofilm pH, EPS content, and biofilm structure by scanning electron microscopy and confocal laser scanning microscopy (CLSM). Substrate surfaces were analyzed by 3D laser scanning confocal microscope.

RESULTS

Enamel surface showed a higher amount of EPS content (p < 0.05), which may be explained by the higher bacterial biomass compared to Ti material. EPS content reduced bacterial susceptibility against antimicrobial treatments for both substrates, compared to EPS control (p < 0.05). However, sucrose-treated cells presented the same magnitude of reduction for Ti or enamel. Interestingly, matrix-enriched biofilms favored bacterial recolonization for both substrates.

CONCLUSION

The surface where the biofilm is growing modulates the amount of EPS synthesized and matrix content plays a key role in reducing antimicrobial susceptibility and promoting bacterial recolonization.

Microplastics act as a carrier for wastewater-borne pathogenic bacteria in sewage

Microplastic pollution, a pressing global environmental problem, has a severe impact on both aquatic ecosystems and public health worldwide. Due to the small size of microplastics, they are able to pass through the filtration systems of municipal wastewater treatment works (WWTWs). In recent years, studies have focused on the environmental abundance and ecotoxicological effects of microplastics, but there are limited studies investigating the colonization of microplastics by bacteria, especially those pathogenic ones. In this study, we examined the colonization and composition of the bacterial communities on polyethylene microbeads after incubation in raw sewage collected from three municipal WWTWs in Hong Kong (Sha Tin Sewage Treatment Works, Stonecutters Island Sewage Treatment Works, and Shek Wu Hui Sewage Treatment Works). Scanning electron microscopy (SEM) results indicate that bacterial cells were colonized on the surfaces of the microbeads and formed biofilms after sewage incubation. Metagenomic sequencing data demonstrated an increase in bacterial diversity after 21 days of sewage incubation when compared to shorter incubation periods of 6, 11 and 16 days. Importantly, human and fish pathogens such as Arcobacter cryaerophilus, Aeromonas salmonicida, Vibrio areninigrae and Vibrio navarrensis were found in the resident bacterial communities. Taken together, our results demonstrate that microplastics could act as a carrier for wastewater-borne pathogenic bacteria in municipal sewage.

Heme cross-feeding can augment Staphylococcus aureus and Enterococcus faecalis dual species biofilms

The contribution of biofilms to virulence and as a barrier to treatment is well-established for Staphylococcus aureus and Enterococcus faecalis, both nosocomial pathogens frequently isolated from biofilm-associated infections. Despite frequent co-isolation, their interactions in biofilms have not been well-characterized. We report that in combination, these two species can give rise to augmented biofilms biomass that is dependent on the activation of E. faecalis aerobic respiration. In E. faecalis, respiration requires both exogenous heme to activate the cydAB-encoded heme-dependent cytochrome bd, and the availability of O₂. We determined that the ABC transporter encoded by cydDC contributes to heme import. In dual species biofilms, S. aureus provides the heme to activate E. faecalis respiration. S. aureus mutants deficient in heme biosynthesis were unable to augment biofilms whereas heme alone is sufficient to augment E. faecalis mono-species biofilms. Our results demonstrate that S. aureus-derived heme, likely in the form of released hemoproteins, promotes E. faecalis biofilm formation, and that E. faecalis gelatinase activity facilitates heme extraction from hemoproteins. This interspecies interaction and metabolic cross-feeding may explain the frequent co-occurrence of these microbes in biofilm-associated infections.

Engineering microbial consortia with rationally designed cellular interactions

Synthetic microbial consortia represent a frontier of synthetic biology that promises versatile engineering of cellular functions. They are primarily developed through the design and construction of cellular interactions that coordinate individual dynamics and generate collective behaviors. Here we review recent advances in the engineering of synthetic communities through cellular-interaction programming. We first examine fundamental building blocks for intercellular communication and unidirectional positive and negative interactions. We then recap the assembly of the building blocks for creating bidirectional interactions in two-species ecosystems, which is followed by the discussion of engineering toward complex communities with increasing species numbers, under spatial contexts, and via model-guided design. We conclude by summarizing major challenges and future opportunities of engineered microbial ecosystems.

Is atomic layer deposition of silver possible on N95 masks?

Due to the COVID19 outbreak, there has been increasing interest in tailoring, modifying and improving conventional personal protective equipment to increase their service life and make them more effective against viruses and bacteria. Here, atomic layer deposition (ALD) was used to functionalize the filter of N95 mask with nano-islands of silver. X-ray photoelectron spectroscopy and x-ray absorption fine structure were used for ALD silver characterization; microbiological assay was conducted to study the effectiveness of the deposited silver against the air-borne pathogen Staphylococcus aureus (S. aureus). Results showed that silver ALD successfully functionalized the N95 mask at 90 and 120 °C for two different numbers of ALD cycles (1100 and 1500 cycles). The deposited silver nano-islands were stable on the N95 filter media against washing. The leaching of silver nano-islands was studied using inductively coupled plasma mass spectrometry of phosphate-buffered saline solution after soaking the mask in it over predetermined times. <9% of Ag was removed after a maximum time of 4 h that was investigated. Antimicrobial tests showed that for samples functionalized with 1100 ALD cycles of Ag, 76% reduction in S. aureus colony-forming units content was observed after 24 h of biofilm development on the mask surfaces.

Microwaves, a potential treatment for bacteria: A review

Bacteria have brought great harm to the public, especially after the emergence of multidrug-resistant bacteria. This has rendered traditional antibiotic therapy ineffective. In recent years, hyperthermia has offered new treatments to remove bacteria. Microwaves (MW) are a component of the electromagnetic spectrum and can rapidly heat materials. Taking advantage of this characteristic of MW, related studies have shown that both thermal and non-thermal effects of MW can inactivate various bacteria. Even though the understanding of MW in the field of bacteria is not sufficient for widespread use at present, MW has performed well in dealing with microorganisms and controlling infection. This review will focus on the application of MW in bacteria and discuss the advantages, prospects and challenges of using MW in the bacterial field.

Effects of the Sex Steroid Hormone Estradiol on Biofilm Growth of Cystic Fibrosis Pseudomonas aeruginosa Isolates

Women with cystic fibrosis (CF) have a significantly lower life expectancy compared to men, which is indicated by an earlier impairment of lung function due to chronic colonization with biofilm formed by Pseudomonas aeruginosa. There is growing evidence that blood serum concentrations of the steroid sex hormone estradiol (E₂) correlate with the occurrence of pulmonary exacerbations in CF but also play a role in the mucoid switch of P. aeruginosa. This study aims to shed light on possible microbiological reasons for sexual dimorphism in CF by investigating the influence of E₂ on biofilm formation of P. aeruginosa CF isolates. For this purpose, 10 CF isolates of the respiratory tract derived from different CF patients have been treated with E₂ in a microtiter plate biofilm model. Biofilms have been examined by crystal violet assays, field emission scanning electron microscopy (FE-SEM), 3D laser scanning microscopy (LSM), and quorum sensing (QS) reporter assays of the supernatants taken from biofilms. This allowed us to simultaneously investigate the effects of E₂ on attached biofilm mass, biofilm ultrastructure, and QS activity. Upon E₂ treatment, six out of 10 investigated CF isolates showed an increase of attached biofilm mass, whereas biofilms from two tested non-CF laboratory strains (PAO1 and ATCC19660) did not. Moreover, FE-SEM and 3D LSM analyses of the E₂ responsive CF biofilms revealed ultrastructural remodeling of biofilm structure at different scales with increased formation of prominent biofilm spots, enhanced coverage with extracellular polymeric substance (EPS), and extended average surface roughness. QS activity measurements performed in biofilm supernatants via luminescence acyl homoserine lactone (AHL) reporter assays further showed that E₂ treatment may also modulate QS signaling, as shown in an E₂ sensitive CF isolate. Together, our results suggest the biofilm modulating effects of E₂ on various clinical CF isolates that are documented by both biomass and ultrastructural changes of biofilms. The gained new insight into the influence of steroid hormones on P. aeruginosa biofilm phenotypes might pave the way for novel future approaches in personalized medicine based on the patients’ sex and hormonal status.

The Xanthophyll Carotenoid Lutein Reduces the Invasive Potential of Pseudomonas aeruginosa and Increases Its Susceptibility to Tobramycin

Recently, the xanthophyll carotenoid lutein has been qualified as a potential quorum sensing (QS) and biofilm inhibitor against Pseudomonas aeruginosa. To address the potential of this xanthophyll compound as a relevant antivirulence agent, we investigated in depth its impact on the invasion capabilities and aggressiveness of P. aeruginosa PAO1, which rely on the bacterial ability to build and maintain protective barriers, use different types of motilities and release myriad virulence factors, leading to host cell and tissue damages. Our data, obtained on the PAO1 strain, indicate that all-trans lutein (Lut; 22 µM) disrupts biofilm formation and disorganizes established biofilm structure without affecting bacterial viability, while improving the bactericidal activity of tobramycin against biofilm-encapsulated PAO1 cells. Furthermore, this xanthophyll affects PAO1 twitching and swarming motilities while reducing the production of the extracellular virulence factors pyocyanin, elastase and rhamnolipids as well as the expression of the QS-regulated lasB and rhlA genes without inhibiting the QS-independent aceA gene. Interestingly, the expression of the QS regulators rhlR/I and lasR/I is significantly reduced as well as that of the global virulence factor regulator vfr, which is suggested to be a major target of Lut. Finally, an oxidative metabolite of Lut, 3′-dehydrolutein, induces a similar inhibition phenotype. Taken together, lutein-type compounds represent potential agents to control the invasive ability and antibiotic resistance of P. aeruginosa.

Extracellular DNA: A Critical Aspect of Marine Biofilms

Multispecies biofilms represent a pervasive threat to marine-based industry, resulting in USD billions in annual losses through biofouling and microbiologically influenced corrosion (MIC). Biocides, the primary line of defence against marine biofilms, now face efficacy and toxicity challenges as chemical tolerance by microorganisms increases. A lack of fundamental understanding of species and EPS composition in marine biofilms remains a bottleneck for the development of effective, target-specific biocides with lower environmental impact. In the present study, marine biofilms are developed on steel with three bacterial isolates to evaluate the composition of the EPSs (extracellular polymeric substances) and population dynamics. Confocal laser scanning microscopy, scanning electron microscopy, and fluorimetry revealed that extracellular DNA (eDNA) was a critical structural component of the biofilms. Parallel population analysis indicated that all three strains were active members of the biofilm community. However, eDNA composition did not correlate with strain abundance or activity. The results of the EPS composition analysis and population analysis reveal that biofilms in marine conditions can be stable, well-defined communities, with enabling populations that shape the EPSs. Under marine conditions, eDNA is a critical EPS component of the biofilm and represents a promising target for the enhancement of biocide specificity against these populations.

Flexible bioelectronic device fabricated by conductive polymer-based living material

Living materials are worked as an inside collaborative system that could naturally respond to changing environmental conditions. The regulation of bioelectronic processes in living materials could be effective for collecting biological signals and detecting biomarkers. Here, we constructed a living material with conjugated polymers poly[3-(3'-N,N,N-triethylamino-1'-propyloxy)-4-methyl-2,5-thiophene chloride] (PMNT) and Shewanella oneidensis MR-1 biofilm. In addition, the living material was integrated as a flexible bioelectronic device for lactate detection in physiological fluids (sweat, urine, and plasma). Owing to the electroconductivity of conjugated polymers, PMNT could optimize the bioelectronic process in the living material. The collected electrical signal could be wirelessly transferred to a portable smartphone for reading and analyzing. Because lactate is also a biomarker for cancer treatment, the flexible bioelectronic device was further used to detect and count the cancer cells. The proof of the bioelectronic device using conductive polymer-based living material exhibits promising applications in the next-generation personal health monitoring systems.

Environmental and Biological Controls on Sedimentary Bottom Types in the Puquios of the Salar de Llamara, Northern Chile

The Puquios of the Salar de Llamara in the Atacama Desert, northern Chile, is a system of small lakes that is characterized by evaporitic mineral deposition and that commonly hosts microbial communities. This region is known for its extreme aridity, solar irradiance, and temperature fluctuations. The Puquios are a highly diverse ecosystem with a variety of sedimentary bottom types. Our previous results identified electrical conductivity (EC) as a first-order environmental control on bottom types. In the present paper, we extend our analysis to examine the effects of additional environmental parameters on bottom types and to consider reasons for the importance of EC as a control of sedimentology. Our results identify microbially produced extracellular polymeric substances (EPS) as a major player in the determination of bottom types. The relative amounts and properties of EPS are determined by EC. EPS, in turn, determines the consistency of bottom types, exchange of bottom substrate with the overlying water column, and mineral precipitation within the substrate. Low-EC ponds in the Puquios system have flocculent to semi-cohesive bottom types, with low-viscosity EPS that allows for high-exchange with the surrounding waters and mineral precipitation of granular gypsum, carbonate, and Mg–Si clay in close association with microbes. Ponds with elevated EC have bottom types that are laminated and highly cohesive with high-viscosity EPS that restricts the exchange between sediments and the surrounding waters; mineral precipitation in these high-EC ponds includes granular to laminated gypsum, carbonate and Mg–Si, which also form in close association with microbes. Bottom types in ponds with EC above the threshold for thriving benthic microbial communities have insufficient EPS accumulations to affect mineral precipitation, and the dominant mineral is gypsum (selenite). The variations in EPS production throughout the Puquios, associated with heterogeneity in environmental conditions, make the Puquios region an ideal location for understanding the controls of sedimentary bottom types in evaporative extreme environments that may be similar to those that existed on early Earth and beyond.

Evidence on the Use of Mouthwash for the Control of Supragingival Biofilm and Its Potential Adverse Effects

Antimicrobial mouthwash improves supragingival biofilm control when used in conjunction with mechanical removal as part of an oral hygiene routine. Mouthwash is intended to suppress bacterial adhesion during biofilm formation processes and is not aimed at mature biofilms. The most common evidence-based effects of mouthwash on the subgingival biofilm include the inhibition of biofilm accumulation and its anti-gingivitis property, followed by its cariostatic activities. There has been no significant change in the strength of the evidence over the last decade. A strategy for biofilm control that relies on the elimination of bacteria may cause a variety of side effects. The exposure of mature oral biofilms to mouthwash is associated with several possible adverse reactions, such as the emergence of resistant strains, the effects of the residual structure, enhanced pathogenicity following retarded penetration, and ecological changes to the microbiota. These concerns require further elucidation. This review aims to reconfirm the intended effects of mouthwash on oral biofilm control by summarizing systematic reviews from the last decade and to discuss the limitations of mouthwash and potential adverse reactions to its use. In the future, the strategy for oral biofilm control may shift to reducing the biofilm by detaching it or modulating its quality, rather than eliminating it, to preserve the benefits of the normal resident oral microflora.

The Response and Survival Mechanisms of Staphylococcus aureus under High Salinity Stress in Salted Foods

Staphylococcus aureus (S. aureus) has a strong tolerance to high salt stress. It is a major reason as to why the contamination of S. aureus in salted food cannot be eradicated. To elucidate its response and survival mechanisms, changes in the morphology, biofilm formation, virulence, transcriptome, and metabolome of S. aureus were investigated. IsaA positively regulates and participates in the formation of biofilm. Virulence was downregulated to reduce the depletion of nonessential cellular functions. Inositol phosphate metabolism was downregulated to reduce the conversion of functional molecules. The MtsABC transport system was downregulated to reduce ion transport and signaling. Aminoacyl-tRNA biosynthesis was upregulated to improve cellular homeostasis. The betaine biosynthesis pathway was upregulated to protect the active structure of proteins and nucleic acids. Within a 10% NaCl concentration, the L-proline content was upregulated to increase osmotic stability. In addition, 20 hub genes were identified through an interaction analysis. The findings provide theoretical support for the prevention and control of salt-tolerant bacteria in salted foods.

Modification of expanded clay carrier for enhancing the immobilization and nitrogen removal capacity of nitrifying and denitrifying bacteria in the aquaculture system

In aquaculture systems, the treatment of nitrogen pollution has always been a center of attention due to its impact on productiveness. The bioremediation method based on simultaneous nitrification and denitrification was often used to effectively remove ammonium, nitrite, and nitrate compounds. In addition, the attachment and biofilm formation of the nitrogen-converting bacteria on carriers had superior removal efficiency over the suspended bacteria. Thus, this study focused on the fabrication of a porosity floatable expanded clay (EC) carrier that provided the basic structure for the immobilization of the nitrifiers Nitrosomonas sp., Nitrobacter sp., and the denitrifier Bacillus sp. The EC was also coated with alginate and essential nutrient to support the cohesion and growth of bacteria. Especially, the selected Bacillus sp. previously proved was able to reduce nitrite/nitrate in aerobic conditions. The co-immobilization of these three aerobic bacteria on the prepared carrier would simply the treatment process in practical use. Initial results showed that the integration of essential nutrients (N, P, K) on alginate coated EC (EC_Alg_N) increased bacterial density to (57 ± 3) × 10⁷ - (430 ± 30) × 10⁸ CFU/g, which then led to the enhancement of removal efficiency up to 91.62 ± 0.67% in the medium containing initial nitrogen content of 60 mg-N/L. The nitrogen removal efficacy of bacterial immobilized EC_Alg_N remained at 83.95 ± 0.15% after being reused for 6 cycles. In conclusion, the bacterial immobilized EC_Alg_N could be a potential material for nitrogen polluted wastewater treatment in aquaculture systems.

Evaluation of antibiotic combination of Litsea cubeba essential oil on Vibrio parahaemolyticus inhibition mechanism and anti-biofilm ability

Vibrio parahaemolyticus (V. parahaemolyticus) is a common pathogen in seafood. The use of antibiotics is a primary tool to prevent and control V. parahaemolyticus in the aquaculture industry. However, V. parahaemolyticus combats the damage caused by antibiotics by forming biofilms under certain conditions. In this study, we analyzed the antibacterial effect and the characteristics of V. parahaemolyticus by experimentally determining the minimum inhibitory concentration (MIC) and the fractional inhibitory concentration index (FICI) values of a combination of the Litsea cubeba essential oil (LCEO) and several commonly used V. parahaemolyticus antibiotics. The bactericidal effect of the essential oil alone and essential oil in combination with the antibiotics were evaluated with time-kill curves. The damage to cell membranes and cell walls were assessed by measuring the content of macromolecules and alkaline phosphatase (AKP) released into the supernatant using V. parahaemolyticus ATCC17802 as the experimental strain. The membrane structure was observed by transmission electron microscopy. The results showed that the MIC value of the LCEO was 1,024 μg/mL, and the LCEO FICI values in combination with tetracycline or oxytetracycline hydrochloride was 0.3125 and 0.75, respectively, indicating synergistic and additive effects. Moreover, LCEO inhibited the growth and promoted the removal of biofilms by reducing the content of hydrophobic and extracellular polysaccharides on the cell surface. This study provides a reference for studying the antibacterial activity of LCEO and the combination of antibiotics to prevent and control the formation of biofilms by V. parahaemolyticus.

Bacteriophage-Mediated Control of Biofilm: A Promising New Dawn for the Future

Biofilms are complex microbial microcolonies consisting of planktonic and dormant bacteria bound to a surface. The bacterial cells within the biofilm are embedded within the extracellular polymeric substance (EPS) consisting mainly of exopolysaccharides, secreted proteins, lipids, and extracellular DNA. This structural matrix poses a major challenge against common treatment options due to its extensive antibiotic-resistant properties. Because biofilms are so recalcitrant to antibiotics, they pose a unique challenge to patients in a nosocomial setting, mainly linked to lower respiratory, urinary tract, and surgical wound infections as well as the medical devices used during treatment. Another unique property of biofilm is its ability to adhere to both biological and man-made surfaces, allowing growth on human tissues and organs, hospital tools, and medical devices, etc. Based on prior understanding of bacteriophage structure, mechanisms, and its effects on bacteria eradication, leading research has been conducted on the effects of phages and its individual proteins on biofilm and its role in overall biofilm removal while also revealing the obstacles this form of treatment currently have. The expansion in the phage host-species range is one that urges for improvement and is the focus for future studies. This review aims to demonstrate the advantages and challenges of bacteriophage and its components on biofilm removal, as well as potential usage of phage cocktail, combination therapy, and genetically modified phages in a clinical setting.

Biofilm-mediated bioremediation is a powerful tool for the removal of environmental pollutants

Biofilm-mediated bioremediation is an attractive approach for the elimination of environmental pollutants, because of its wide adaptability, biomass, and excellent capacity to absorb, immobilize, or degrade contaminants. Biofilms are assemblages of individual or mixed microbial cells adhering to a living or non-living surface in an aqueous environment. Biofilm-forming microorganisms have excellent survival under exposure to harsh environmental stressors, can compete for nutrients, exhibit greater tolerance to pollutants compared to free-floating planktonic cells, and provide a protective environment for cells. Biofilm communities are thus capable of sorption and metabolization of organic pollutants and heavy metals through a well-controlled expression pattern of genes governed by quorum sensing. The involvement of quorum sensing and chemotaxis in biofilms can enhance the bioremediation kinetics with the help of signaling molecules, the transfer of genetic material, and metabolites. This review provides in-depth knowledge of the process of biofilm formation in microorganisms, their regulatory mechanisms of interaction, and their importance and application as powerful bioremediation agents in the biodegradation of environmental pollutants, including hydrocarbons, pesticides, and heavy metals.

Chronic Inflammation in Non-Healing Skin Wounds and Promising Natural Bioactive Compounds Treatment

Chronic inflammation is one of the hallmarks of chronic wounds and is tightly coupled to immune regulation. The dysregulation of the immune system leads to continuing inflammation and impaired wound healing and, subsequently, to chronic skin wounds. In this review, we discuss the role of the immune system, the involvement of inflammatory mediators and reactive oxygen species, the complication of bacterial infections in chronic wound healing, and the still-underexplored potential of natural bioactive compounds in wound treatment. We focus on natural compounds with antioxidant, anti-inflammatory, and antibacterial activities and their mechanisms of action, as well as on recent wound treatments and therapeutic advancements capitalizing on nanotechnology or new biomaterial platforms.

Microbiota-Associated Biofilm Regulation Leads to Vibrio cholerae Resistance Against Intestinal Environmental Stress

The commensal microbes of the gut microbiota make important contributions to host defense against gastrointestinal pathogens, including Vibrio cholerae, the etiologic agent of cholera. As interindividual microbiota variation drives individual differences in infection susceptibility, we examined both host and V. cholerae gene expression during infection of suckling mice transplanted with different model human commensal communities, including an infection-susceptible configuration representing communities damaged by recurrent diarrhea and malnutrition in cholera endemic areas and a representative infection-resistant microbiota characteristic of healthy individuals. In comparison to colonization of animals with resistant microbiota, animals bearing susceptible microbiota challenged with V. cholerae downregulate genes associated with generation of reactive oxygen/nitrogen stress, while V. cholerae in these animals upregulates biofilm-associated genes. We show that V. cholerae in susceptible microbe infection contexts are more resistant to oxidative stress and inhibitory bile metabolites generated by the action of commensal microbes and that both phenotypes are dependent on biofilm-associated genes, including vpsL. We also show that susceptible and infection-resistant microbes drive different bile acid compositions in vivo by the action of bile salt hydrolase enzymes. Taken together, these findings provide a better understanding of how the microbiota uses multiple mechanisms to modulate the infection-associated host environment encountered by V. cholerae, leading to commensal-dependent differences in infection susceptibility.

Stress response modulation: the key to survival of pathogenic and spoilage bacteria during poultry processing

The control of bacterial contaminants on meat is a key area of interest in the food industry. Bacteria are exposed to a variety of stresses during broiler processing which challenge bacterial structures and metabolic pathways causing death or sublethal injury. To counter these stresses, bacteria possess robust response systems that can induce shifts in the transcriptome and proteome to enable survival. Effective adaptive responses, such as biofilm formation, shock protein production and metabolic flexibility, require rapid induction and implementation at a cellular and community level to facilitate bacterial survival in adverse conditions. This review aims to provide an overview of the scientific literature pertaining to the regulation of complex adaptive processes used by bacteria to survive the processing environment, with particular focus on species that impact the quality and safety of poultry products like Campylobacter spp., Salmonella enterica and Pseudomonas spp.

EFFICACY OF CURCUMIN-MEDIATED ANTIBACTERIAL PHOTODYNAMIC THERAPY FOR ORAL ANTISEPSIS: A SYSTEMATIC REVIEW AND NETWORK META-ANALYSIS OF RANDOMIZED CLINICAL TRIALS

BACKGROUND

currently, the presence of oral microorganisms resistant to traditional treatment is increasing, thus search for new modalities of therapies is needed. In this context, antimicrobial photodynamic therapy (aPDT) is an alternative approach for the treatment of resistant or not resistant microorganisms. Therefore, the aim of the present study was to conduct a systematic review and meta-analysis of randomized clinical trials of aPDT for oral antisepsis against oral polymicrobial biofilms.

METHODS

PubMed, Science Direct, Scopus, SciELO, Lilacs, Cochrane Library and Embase databases were searched. In total, five articles were included for qualitative analysis and four articles were used for quantitative analyses. Bias assessment of the eligible articles was made using the RoB 2 criteria. Network meta-analysis was performed using the random-effect model. Subgroup's analysis was also conducted. The groups evaluated were aPDT, exposure to light only and no treatment at all (control group). The quality of evidence was accessed by CINeMA approach.

RESULTS

aPDT mediated by curcumin had significant results in the reducing bacterial load (0.31-0.49 log₁₀ UFC/ I²=0%) when compared with the control group. The included articles were classified as low risk of bias, despite biases detected by allocation and blinding. Moreover, quantitative analysis between aPDT and control group and between light and control group were classified with low risk of confidence rating, while the results from aPDT versus light were classified as moderate risk of confidence rating.

CONCLUSION

aPDT has significant efficacy for oral antisepsis, however more randomized clinical trials will be needed to validate the present results.

Exploiting the Anti-Biofilm Effect of the Engineered Phage Endolysin PM-477 to Disrupt In Vitro Single- and Dual-Species Biofilms of Vaginal Pathogens Associated with Bacterial Vaginosis

Bacterial vaginosis (BV) is the most frequent vaginal infection in women of reproductive age. It is caused by the overgrowth of anaerobic vaginal pathogens, such as Gardnerella vaginalis, Fannyhessea vaginae, and Prevotella bivia, which are vaginal pathogens detected during the early stages of incident BV and have been found to form multi-species biofilms. Treatment of biofilm-associated infections, such as BV, is challenging. In this study, we tested the role of an investigational engineered phage endolysin, PM-477, in the eradication of dual-species biofilms composed of G. vaginalis–F. vaginae or G. vaginalis–P. bivia. Single-species biofilms formed by these species were also analysed as controls. The effect of PM-477 on biomass and culturability of single- and dual-species biofilms was assessed in vitro using a microtiter plate assay, epifluorescence microscopy, confocal laser scanning microscopy, and quantitative PCR. The results showed that PM-477 was particularly effective in the disruption and reduction of culturability of G. vaginalis biofilms. In dual-species biofilms, PM-477 exhibited lower efficiency but was still able to selectively and significantly eliminate G. vaginalis. Since polymicrobial interactions have been shown to strongly affect the activity of various antibiotics, the activity of PM-477 in dual-species biofilms is a potentially promising result that should be further explored, aiming to completely eradicate multi-species biofilms associated with BV.

The Type VI Secretion Systems in Plant-Beneficial Bacteria Modulate Prokaryotic and Eukaryotic Interactions in the Rhizosphere

Rhizosphere colonizing plant growth promoting bacteria (PGPB) increase their competitiveness by producing diffusible toxic secondary metabolites, which inhibit competitors and deter predators. Many PGPB also have one or more Type VI Secretion System (T6SS), for the delivery of weapons directly into prokaryotic and eukaryotic cells. Studied predominantly in human and plant pathogens as a virulence mechanism for the delivery of effector proteins, the function of T6SS for PGPB in the rhizosphere niche is poorly understood. We utilized a collection of Pseudomonas chlororaphis 30-84 mutants deficient in one or both of its two T6SS and/or secondary metabolite production to examine the relative importance of each T6SS in rhizosphere competence, bacterial competition, and protection from bacterivores. A mutant deficient in both T6SS was less persistent than wild type in the rhizosphere. Both T6SS contributed to competitiveness against other PGPB or plant pathogenic strains not affected by secondary metabolite production, but only T6SS-2 was effective against strains lacking their own T6SS. Having at least one T6SS was also essential for protection from predation by several eukaryotic bacterivores. In contrast to diffusible weapons that may not be produced at low cell density, T6SS afford rhizobacteria an additional, more immediate line of defense against competitors and predators.

High burden and diversity of carbapenemase-producing Enterobacterales observed in wastewater of a tertiary care hospital in Germany

Hospitals are one of the main reservoirs of multi-resistant Enterobacterales (MRE). As MRE are resistant to the most frequently used antibiotics, therapy for patients with MRE infections is challenging. It has been previously described that MRE from hospital wastewater can pass into municipal wastewater and even surface water. In this study, we investigated the diversity and epidemiology of MRE in the wastewater of a large tertiary care hospital. Wastewater samples were collected for a four-day period and tested for the presence of Enterobacterales resistant to 3rd gen. cephalosporins. Representative isolates were further characterized by whole genome sequencing. In 120 β-glucuronidase-producing isolates, 68 Escherichia coli and, interestingly, also 52 Citrobacter freundii were identified. In 120 β-glucosidase-producing isolates 45 Serratia marcescens, 34 Klebsiella oxytoca, 32 Enterobacter cloacae and 9 Klebsiella pneumoniae were observed. For all species various MLST sequence types and different clusters of resistance genes were determined, showing a great diversity within the different Enterobacterales, further corroborated by clonal analysis performed by cgMLST. The most prominent clone was wastewater associated E. coli ST635, which accounted for 47.1% of all E. coli isolates. Interestingly, 45.6% of E. coli, 88.5% of C. freundii, 95.6% of S. marcescens, 91.2% of K. oxytoca, 96.9% of E. cloacae and 88.9% of K. pneumoniae isolates carried a carbapenemase gene, indicating a high burden with carbapenemase-producing Enterobacterales. Comparison with clinical isolates from the same hospital displayed few clonal matches. One wastewater isolate of K. pneumoniae was identified to be closely related compared to a clone that had been introduced into the hospital during an outbreak four years earlier. One E. coli isolate was identified as identical to an isolate from a patient, with inpatient stay during the sampling period. The data obtained in this study highlight the problem of antibiotic resistance of Enterobacterales in hospital wastewater. In particular, the clustered occurrence of carbapenemase genes is of great concern and underscores the problem of increasingly scarce antibiotic options against these bacteria.

Metabolism of the Genus Guyparkeria Revealed by Pangenome Analysis

Halophilic sulfur-oxidizing bacteria belonging to the genus Guyparkeria occur at both marine and terrestrial habitats. Common physiological characteristics displayed by Guyparkeria isolates have not yet been linked to the metabolic potential encoded in their genetic inventory. To provide a genetic basis for understanding the metabolism of Guyparkeria, nine genomes were compared to reveal the metabolic capabilities and adaptations. A detailed account is given on Guyparkeria’s ability to assimilate carbon by fixation, to oxidize reduced sulfur, to oxidize thiocyanate, and to cope with salinity stress.

Pre-incubation conditions determine the fermentation pattern and microbial community structure in fermenters at mild hydrostatic pressure

Fermentation at elevated hydrostatic pressure is a novel strategy targeting product selectivity. However, the role of inoculum history and cross-resistance, that is, acquired tolerance from incubation under distinctive environmental stress, remains unclear in high-pressure operation. In our here presented work, we studied fermentation and microbial community responses of halotolerant marine sediment inoculum (MSI) and anaerobic digester inoculum (ADI), pre-incubated in serum bottles at different temperatures and subsequently exposed to mild hydrostatic pressure (MHP; < 10 MPa) in stainless steel reactors. Results showed that MHP effects on microbial growth, activity, and community structure were strongly temperature-dependent. At moderate temperature (20°C), biomass yield and fermentation were not limited by MHP; suggesting a cross-resistance effect from incubation temperature and halotolerance. Low temperatures (10°C) and MHP imposed kinetic and bioenergetic limitations, constraining growth and product formation. Fermentation remained favorable in MSI at 28°C and ADI at 37°C, despite reduced biomass yield resulting from maintenance and decay proportionally increasing with temperature. Microbial community structure was modified by temperature during the enrichment, and slight differences observed after MHP-exposure did not compromise functionality. Results showed that the relation incubation temperature-halotolerance proved to be a modifier of microbial responses to MHP and could be potentially exploited in fermentations to modulate product/biomass ratio.

Recent advances in plastic degradation - From microbial consortia-based methods to data sciences and computational biology driven approaches

The conventional methods of plastic waste management such as mechanical and chemical recycling, landfill complemented by incineration and pyrosis have limited scope. Thus, microbiological-based approaches by the application of microbial consortia or cocultures are appropriate, cost-effective, and eco-friendly to manage plastic wastes. Screening of novel plastic degrading microorganisms, the formulation of microbial consortia, and utilisation of their enzymes probably play a role in plastic waste management. The by-products of microbial degradation of plastic waste can be used as bio-energy sources, that aids in the development of cost-effective bio-digesters. The recent advancements in computational biology and bioinformatics play a vital role in understanding the molecular basis of enzymatic degradation of plastic polymers by microorganisms. Understanding the three-dimensional structures of plastic degrading enzymes and their metabolic pathways play a vital role in studying the microbial degradation of plastics. The present review highlights the scope of various microorganisms and their enzymes in plastic degradation. The review emphasizes the applications of co-cultures or microbial consortia-based approaches for the enhanced degradation of plastic polymers and the production of value-added end products that can be used as the prototypes of bioenergy sources. The review also provides a comprehensive outlook on the applications of data sciences, computational biology, and bioinformatics resources, and web-based tools towards the study of microbial degradation of plastic polymers.

A Potential “Vitaminic Strategy” against Caries and Halitosis

Streptococcus mutans and Fusobacterium nucleatum are two key bacteria of the oral microbiota. Due to their ability to form biofilms on oral tissues, they are both involved in the onset of the most common oral diseases. F. nucleatum is also the principal producer of hydrogen sulfide (H2S), causative of the awkward bad breath of halitosis. In this study, the oral product Vea® Oris, made by vitamin E and capric/caprylic acid only, was evaluated as a potential treatment for the most common oral diseases. Different concentrations of the product were tested against both S. mutans and F. nucleatum. The effect on planktonic and biofilm growth was investigated for both strains, and for F. nucleatum, the influence on H2S production was evaluated. From our data, the product did not relevantly reduce the planktonic growth of both strains, whereas it validly counteracted biofilm assemblage. Moreover, an interesting trend of H2S reduction was highlighted. Overall, these results suggested, on the one hand, a synergistic antimicrobial–antibiofilm action of two Vea® Oris components and, together, potential modulation activity on H2S production. However, the study should be implemented to confirm these only preliminary findings, certainly extending the panel of tested bacteria and using alternative methods of detection.

Antibacterial Activity of Isobavachalcone (IBC) Is Associated with Membrane Disruption

Isobavachalcone (IBC) is a natural prenylated chalcone with a broad spectrum of pharmacological properties. In this work, we newly synthesized and investigated the antibacterial activity of IBC against Gram-positive, Gram-negative and mycobacterial species. IBC was active against Gram-positive bacteria, mainly against Methicillin-Susceptible Staphylococcus aureus (MSSA) and Methicillin-Resistant Staphylococcus aureus (MRSA), with minimum inhibitory concentration (MIC) values of 1.56 and 3.12 µg/mL, respectively. On the other hand, IBC was not able to act against Gram-negative species (MIC > 400 µg/mL). IBC displayed activity against mycobacterial species (MIC = 64 µg/mL), including Mycobacterium tuberculosis, Mycobacterium avium and Mycobacterium kansasii. IBC was able to inhibit more than 50% of MSSA and MRSA biofilm formation at 0.78 µg/mL. Its antibiofilm activity was similar to vancomycin, which was active at 0.74 µg/mL. In order to study the mechanism of the action by fluorescence microscopy, the propidium iodide (PI) and SYTO9 fluorophores indicated that IBC disrupted the membrane of Bacillus subtilis. Toxicity assays using human keratinocytes (HaCaT cell line) showed that IBC did not have the capacity to reduce the cell viability. These results suggested that IBC is a promising antibacterial agent with an elucidated mode of action and potential applications as an antibacterial drug and a medical device coating.

Validation of housekeeping genes as internal controls for gene expression studies on biofilm formation in Bacillus velezensis

Bacillus velezensis is an important bacterium widely applied in agriculture and industry, and biofilms play critical roles in its environmental tolerance. The appropriate choice of reference genes is essential for key gene expression studies. Multiple internal control genes were selected and validated from the 21 housekeeping genes of B. velezensis by expression stability evaluation during biofilm formation and were used to study the expression of key genes involved in the process. The results showed that pyk, gyrA, recA, and gyrB were stably expressed, and the expression of pyk was the most stable during biofilm formation. A pair of two genes, pyk and gyrA, provided high-quality data when used as internal controls, and the combination of three genes, pyk, gyrA, and recA, was even better. The expression levels of pyk, gyrA, and recA approximated those of five key genes, abrB, epsD, kinC, sinR, and tasA, in biofilm formation, meeting the requirements of ideal internal control genes. The expression patterns of 5 key genes were studied with 16S, pyk, the pair of 2 genes, pyk and gyrA, and the combination of 3 genes, pyk, gyrA, and recA, as internal controls during the biofilm formation process. The results proved that pyk was a suitable internal control, as were the pair of 2 genes, pyk and gyrA, and the combination of 3 genes, pyk, gyrA, and recA. This study provided genes and gene combinations which were validated as suitable internal controls for gene expression studies, especially those on the mechanism of biofilm formation in B. velezensis or even other Bacillus spp. KEY POINTS: • Reference genes is necessary for gene expression study in biofilm formation of Bacillus velezensis • Pyk and 2 gene combinations were selected and validated from 21 common used genes • Expression of key genes in biofilm formation was normalized with the selected internal controls.

Kassporin-KS1: A Novel Pentadecapeptide from the Skin Secretion of Kassina senegalensis: Studies on the Structure-Activity Relationships of Site-Specific “Glycine-Lysine” Motif Insertions

Due to the abuse of traditional antibiotics and the continuous mutation of microbial resistance genes, microbial infections have become serious problems for human health. Therefore, novel antibacterial agents are urgently required, and amphibian antimicrobial peptides (AMP) are among the most interesting potential antibacterial leads. In this research, a novel peptide, named kassporin-KS1 (generically QUB-1641), with moderate antibacterial activity against Gram-positive bacteria, was discovered in the skin secretion of the Senegal running frog, Kassina senegalensis. Using site-specific sequence enrichment with a motif “glycine-lysine” that frequently occurs in ranid frog temporin peptides, a series of QUB-1641 analogues were synthesized, and effects on selected bioactivities were studied. The greatest activity enhancement was obtained when the “glycine-lysine” motif was located at the eighth and ninth position as in QUB-1570.QUB-1570 had a broader antibacterial spectrum than QUB-1641, and was eight-fold more potent. Moreover, QUB-1570 inhibited S. aureus biofilm most effectively, and significantly enhanced the viability of insect larvae infected with S. aureus. When the “glycine-lysine” motif of QUB-1570 was substituted to reduce the helix ratio and positive charge, the antibacterial activities of these synthetic analogues decreased. These data revealed that the “glycine-lysine” motif at positions 8 and 9 had the greatest enhancing effect on the antibacterial properties of QUB-1570 through increasing positive charge and helix content. This research may provide strategies for the site’s selective amino acid modification of some natural peptides to achieve the desired enhancement of activity.

Inhibition and disintegration of Bacillus subtilis biofilm with small molecule inhibitors identified through virtual screening for targeting TasA(28-261), the major protein component of ECM

Microbial biofilms have been recognized for a vital role in antibiotic resistance and chronic microbial infections for 2-3 decades; still, there are no 'anti-biofilm drugs' available for human applications. There is an urgent need to develop novel 'anti-biofilms' therapeutics to manage biofilm-associated infectious diseases. Several reports have suggested that targeting molecules involved in quorum sensing or biofilm-specific transcription may inhibit biofilm formation. However, the possibility of targeting other vital components of microbial biofilms, especially the extracellular matrix (ECM) components, has remained largely unexplored. Here we report targeting TasA_(28-261), the major proteinaceous component of Bacillus subtilis ECM with two small molecule inhibitors (lovastatin and simvastatin) identified through virtual screening and drug repurposing, resulted in complete inhibition of biofilm. In molecular docking and dynamics simulation studies, lovastatin was observed to make stable interactions with TasA_(28-261), whereas the simvastatin - TasA_(28-261) interactions were relatively less stable. However, in subsequent in vitro studies, both lovastatin and simvastatin successfully inhibited B. subtilis biofilm formation at MIC values of < 10 µg/ml. Besides, these potential inhibitors also caused the disintegration of pre-formed biofilms. Results presented here provide 'proof of concept' for the hypothesis that targeting the extracellular matrix's vital component(s) could be one of the most efficient approaches for inhibiting microbial biofilms and disintegrating the pre-formed biofilms. We propose that a similar approach targeting ECM-associated proteins with FDA-approved drugs could be implemented to develop novel anti-biofilm therapeutic strategies against biofilm-forming chronic microbial pathogens.Communicated by Ramaswamy H. Sarma.

Expanded validation of the effect and quality of a pathogen inactivation system based on riboflavin photochemistry on platelet bacterial contamination

Background

Bacterial contamination still poses serious challenges to blood safety. Platelets have the highest bacterial contamination risk of all blood components.

Methods

Twenty units of manual platelets were prepared from blood donated by our hospital, which were inoculated with Staphylococcus aureus and Escherichia coli suspensions. The riboflavin sodium phosphate solution was added into platelets, adjusted to a final concentration of 160 μmol/L. Platelets added into an illumination bag and placed in the inactivation system for riboflavin photochemistry at various doses. The inactivation effect of bacteria was evaluated on a Columbia blood agar plate by the plate counting method. Meanwhile, the blood routine, blood gas analysis, platelet aggregation test, and thromboelastogram of platelets before and after treatment were detected to evaluate the changes of platelet quality after treatment.

Results

the inactivation effect of S. aureus and E. coli at the inactivation dose (16.9 J/cm²) could reach more than 4 logs. After treatment at 16.9 J/cm², the blood routine results showed that the platelet count was significantly different (P<0.05), and the blood gas analysis showed that the oxygen partial pressure (pO₂) and lactic acid concentration (cLac) were also significantly different (P<0.05). After 16.9 J/cm² treatment, there was a significant difference between Arachidonic acid (AA) and Collagen (Cog) activator groups in the platelet aggregation experiment (P<0.05), but there was no significant difference in the main thrombelastogram (TEG) parameters (R value, K value, angle value, MA value) after treatment (P>0.05).

Conclusions

The inactivation effect of this set of blood component pathogen inactivation system on platelet bacterial contamination could be considered to meet actual clinical needs, with the inactivation treatment having little impact on platelet function.

Microbial adaptation to different environmental conditions: molecular perspective of evolved genetic and cellular systems

Microorganisms are ubiquitous on Earth and can inhabit almost every environment. In a complex heterogeneous environment or in face of ecological disturbance, the microbes adjust to fluctuating environmental conditions through a cascade of cellular and molecular systems. Their habitats differ from cold microcosms of Antarctica to the geothermal volcanic areas, terrestrial to marine, highly alkaline zones to the extremely acidic areas and freshwater to brackish water sources. The diverse ecological microbial niches are attributed to the versatile, adaptable nature under fluctuating temperature, nutrient availability and pH of the microorganisms. These organisms have developed a series of mechanisms to face the environmental changes and thereby keep their role in mediate important ecosystem functions. The underlying mechanisms of adaptable microbial nature are thoroughly investigated at the cellular, genetic and molecular levels. The adaptation is mediated by a spectrum of processes like natural selection, genetic recombination, horizontal gene transfer, DNA damage repair and pleiotropy-like events. This review paper provides the fundamentals insight into the microbial adaptability besides highlighting the molecular network of microbial adaptation under different environmental conditions.

Deploying Viruses against Phytobacteria: Potential Use of Phage Cocktails as a Multifaceted Approach to Combat Resistant Bacterial Plant Pathogens

Plants in nature are under the persistent intimidation of severe microbial diseases, threatening a sustainable food production system. Plant-bacterial pathogens are a major concern in the contemporary era, resulting in reduced plant growth and productivity. Plant antibiotics and chemical-based bactericides have been extensively used to evade plant bacterial diseases. To counteract this pressure, bacteria have evolved an array of resistance mechanisms, including innate and adaptive immune systems. The emergence of resistant bacteria and detrimental consequences of antimicrobial compounds on the environment and human health, accentuates the development of an alternative disease evacuation strategy. The phage cocktail therapy is a multidimensional approach effectively employed for the biocontrol of diverse resistant bacterial infections without affecting the fauna and flora. Phages engage a diverse set of counter defense strategies to undermine wide-ranging anti-phage defense mechanisms of bacterial pathogens. Microbial ecology, evolution, and dynamics of the interactions between phage and plant-bacterial pathogens lead to the engineering of robust phage cocktail therapeutics for the mitigation of devastating phytobacterial diseases. In this review, we highlight the concrete and fundamental determinants in the development and application of phage cocktails and their underlying mechanism, combating resistant plant-bacterial pathogens. Additionally, we provide recent advances in the use of phage cocktail therapy against phytobacteria for the biocontrol of devastating plant diseases.

Evaluation of Cronobacter sakazakii biofilm formation after sdiA knockout in different osmotic pressure conditions

This study characterizes the impact of sdiA on biofilm formation under normal or osmotic stress conditions in Cronobacter sakazakii by constructing a sdiA deletion mutant (ΔsdiA). Here, the downregulation of flagellar assembly-related genes and upregulation of capsular, cellulose and lipopolysaccharide biosynthesis-associated genes in ΔsdiA were observed when compared to the wild type strain (WT) through transcriptomic analysis. Meanwhile, reduced ability of motility, enhanced cell surface hydrophobicity and stronger biofilms with extracellular matrix were observed in WT with deletion of sdiA. Both WT and ΔsdiA formed more biofilm in low osmotic stress medium, while in hyperosmolarity conditions, formation of biofilm was dramatically reduced. Our findings supported that sdiA might suppress biofilm formation of C. sakazakii by regulating biosynthesis of flagellar and extracellular polymeric substances. This study investigates the role of sdiA on biofilm formation in C. sakazakii, and provides the basis for the inhibition of C. sakazakii in food industry and infant-feeding.

Effect of Fluidized Bed Drying, Matrix Constituents and Structure on the Viability of Probiotic Lactobacillus paracasei ATCC 55544 during Storage at 4 °C, 25 °C and 37 °C

The stabilization of probiotics for application in non-refrigerated food products is a challenging task. In the present study, probiotic Lactobacillus paracasei (Lacticaseibacillus paracasei) ATCC 55544 cells were immobilized in a dairy matrix comprising of whole milk powder, skim milk powder, or milk protein isolate using fluidized bed drying technology. The samples were taken out at different drying stages, with an apparent water activity (a_w) of a_w 0.5, a_w 0.4, and a_w 0.3, respectively, and vacuum-packed to maintain the a_w and stored at three different temperatures of 4 °C, 25 °C, and 37 °C. The study evaluated the impact of matrix constituents, milk fat, protein, and carbohydrate on the viability of encapsulated probiotic L . paracasei ATCC 55544 during storage for 1 month. The whole milk powder matrix provided superior protection to the bacteria. Confocal Laser Scanning Microscopy (CLSM) was used to investigate the structure of the immobilizing matrix and the location of the probiotic L. paracasei cells embedded within the matrix. The CLSM study revealed that the probiotic bacterial cells are mostly embedded as clusters beneath the top layer. We hypothesize that the biofilm-like structure, together with the protective whole milk powder matrix, helps to retain the superior viability of probiotic cells during storage at non-refrigerated storage conditions of 25 °C and 37 °C.