Bacterial lipoproteins are a set of membrane proteins with many different functions. Due to this broad-ranging functionality, these proteins have a considerable significance in many phenomena, from cellular physiology through cell division and virulence. Here we give a general overview of lipoprotein biogenesis and highlight examples of the roles of lipoproteins in bacterial disease caused by a selection of medically relevant Gram-negative and Gram-positive pathogens: Mycobacterium tuberculosis, Streptococcus pneumoniae, Borrelia burgdorferi, and Neisseria meningitidis. Lipoproteins have been shown to play key roles in adhesion to host cells, modulation of inflammatory processes, and translocation of virulence factors into host cells. As such, a number of lipoproteins have been shown to be potential vaccines. This review provides a summary of some of the reported roles of lipoproteins and of how this knowledge has been exploited in some cases for the generation of novel countermeasures to bacterial diseases.

https://iai.asm.org/content/iai/79/2/548.full.pdf

Lipoproteins of Bacterial Pathogens

During long-term cystic fibrosis lung infections, Pseudomonas aeruginosa undergoes genetic adaptation resulting in progressively increased persistence and the generation of adaptive colony morphotypes. This includes small colony variants (SCVs), auto-aggregative, hyper-adherent cells whose appearance correlates with poor lung function and persistence of infection. The SCV morphotype is strongly linked to elevated levels of cyclic-di-GMP, a ubiquitous bacterial second messenger that regulates the transition between motile and sessile, cooperative lifestyles. A genetic screen in PA01 for SCV-related loci identified the yfiBNR operon, encoding a tripartite signaling module that regulates c-di-GMP levels in P. aeruginosa. Subsequent analysis determined that YfiN is a membrane-integral diguanylate cyclase whose activity is tightly controlled by YfiR, a small periplasmic protein, and the OmpA/Pal-like outer-membrane lipoprotein YfiB. Exopolysaccharide synthesis was identified as the principal downstream target for YfiBNR, with increased production of Pel and Psl exopolysaccharides responsible for many characteristic SCV behaviors. An yfi-dependent SCV was isolated from the sputum of a CF patient. Consequently, the effect of the SCV morphology on persistence of infection was analyzed in vitro and in vivo using the YfiN-mediated SCV as a representative strain. The SCV strain exhibited strong, exopolysaccharide-dependent resistance to nematode scavenging and macrophage phagocytosis. Furthermore, the SCV strain effectively persisted over many weeks in mouse infection models, despite exhibiting a marked fitness disadvantage in vitro. Exposure to sub-inhibitory concentrations of antibiotics significantly decreased both the number of suppressors arising, and the relative fitness disadvantage of the SCV mutant in vitro, suggesting that the SCV persistence phenotype may play a more important role during antimicrobial chemotherapy. This study establishes YfiBNR as an important player in P. aeruginosa persistence, and implicates a central role for c-di-GMP, and by extension the SCV phenotype in chronic infections.

/pdf/yfibnr-mediates-cyclic-di-gmp-dependent-small-colony-variant-xhoy1y9db5.pdf

YfiBNR Mediates Cyclic di-GMP Dependent Small Colony Variant Formation and Persistence in Pseudomonas aeruginosa

Antibacterial properties of two-dimensional (2D) nanomaterials are of great interest in fields such as environmental engineering, biomedical engineering, and medicine. Ti3C2Tx MXene, a novel 2D nan...

Antimicrobial Mode-of-Action of Colloidal Ti3C2Tx MXene Nanosheets

The genetic adaptation of pathogens in host tissue plays a key role in the establishment of chronic infections. While whole genome sequencing has opened up the analysis of genetic changes occurring during long-term infections, the identification and characterization of adaptive traits is often obscured by a lack of knowledge of the underlying molecular processes. Our research addresses the role of Pseudomonas aeruginosa small colony variant (SCV) morphotypes in long-term infections. In the lungs of cystic fibrosis patients, the appearance of SCVs correlates with a prolonged persistence of infection and poor lung function. Formation of P. aeruginosa SCVs is linked to increased levels of the second messenger c-di-GMP. Our previous work identified the YfiBNR system as a key regulator of the SCV phenotype. The effector of this tripartite signaling module is the membrane bound diguanylate cyclase YfiN. Through a combination of genetic and biochemical analyses we first outline the mechanistic principles of YfiN regulation in detail. In particular, we identify a number of activating mutations in all three components of the Yfi regulatory system. YfiBNR is shown to function via tightly controlled competition between allosteric binding sites on the three Yfi proteins; a novel regulatory mechanism that is apparently widespread among periplasmic signaling systems in bacteria. We then show that during long-term lung infections of CF patients, activating mutations invade the population, driving SCV formation in vivo. The identification of mutational “scars” in the yfi genes of clinical isolates suggests that Yfi activity is both under positive and negative selection in vivo and that continuous adaptation of the c-di-GMP network contributes to the in vivo fitness of P. aeruginosa during chronic lung infections. These experiments uncover an important new principle of in vivo persistence, and identify the c-di-GMP network as a valid target for novel anti-infectives directed against chronic infections.

/pdf/the-yfibnr-signal-transduction-mechanism-reveals-novel-31ik6kex8j.pdf

The YfiBNR signal transduction mechanism reveals novel targets for the evolution of persistent Pseudomonas aeruginosa in cystic fibrosis airways.

Two-dimensional (2D) nanomaterials have attracted considerable attention in biomedical and environmental applications due to their antimicrobial activity. In the interest of investigating the primary antimicrobial mode-of-action of 2D nanomaterials, we studied the antimicrobial properties of MnO2 and MoS2, toward Gram-positive and Gram-negative bacteria. Bacillus subtilis and Escherichia coli bacteria were treated individually with 100 μg/mL of randomly oriented and vertically aligned nanomaterials for ∼3 h in the dark. The vertically aligned 2D MnO2 and MoS2 were grown on 2D sheets of graphene oxide, reduced graphene oxide, and Ti3C2 MXene. Measurements to determine the viability of bacteria in the presence of the 2D nanomaterials performed by using two complementary techniques, flow cytometry, and fluorescence imaging showed that, while MnO2 and MoS2 nanosheets show different antibacterial activities, in both cases, Gram-positive bacteria show a higher loss in membrane integrity. Scanning electron micro...

Antimicrobial Properties of 2D MnO2 and MoS2 Nanomaterials Vertically Aligned on Graphene Materials and Ti3C2 MXene

The protein Pal (peptidoglycan-associated lipoprotein) is anchored in the outer membrane (OM) of Gram-negative bacteria and interacts with Tol proteins. Tol–Pal proteins form two complexes: the first is composed of three inner membrane Tol proteins (TolA, TolQ and TolR); the second consists of the TolB and Pal proteins linked to the cell's OM. These complexes interact with one another forming a multiprotein membrane-spanning system. It has recently been demonstrated that Pal is essential for bacterial survival and pathogenesis, although its role in virulence has not been clearly defined. This review summarizes the available data concerning the structure and function of Pal and its role in pathogenesis.

http://zgb.biol.uw.edu.pl/files/Godlewska_FEMSMicrobiolLett_2009.pdf

Peptidoglycan-associated lipoprotein (Pal) of Gram-negative bacteria: function, structure, role in pathogenesis and potential application in immunoprophylaxis.

Context
Significant differences exist in the needs of an adult patient and those of a sick child with members of his or her family involved. Monitoring questionnaires of patients and their family members can show ways to improve medical care and develop methods for effective staff behavior. The Consumer Assessment System for Healthcare Service Providers and Systems (CAHPS) helps hospitals, using management data, to identify strengths and weaknesses, determine what needs improvement, and track progress over time.


Objective
The study intended to identify the most effective methods for monitoring patients and their families in pediatric hospitals, which can lead to the achievement of high-level medical care.


Design
The research team performed a narrative review by searching the Agency for Healthcare Research and Quality, PubMed Central, and the National Library of Medicine databases for scientific studies and reports from researchers who have used the innovations from CAHPS in their practices. The search used the keywords children and hospital, improving the quality of service, coordination of care, and medical care.


Setting
The study took place in the Department of Pediatric Hematology, Oncology and Transplantation at the Medical University of Lublin in Lublin, Poland.


Outcome Measures
The research team analyzed the selected studies to find specific, applicable, and successful monitoring methodology.


Results
The study examined many important aspects of the stay of children in a hospital and of the difficulties that young patients and their families face and identified the most effective monitoring methods for various areas that affect the interests of a child and his or her family within the walls of the hospital.


Conclusions
This review provides direction for medical institutions, allowing the possibility of improving the quality of patient monitoring. Researchers have carried out few studies in pediatric hospitals today, and the field needs further study.

Review of Best Practices for Patient Monitoring to Improve the Effectiveness of Therapy in Pediatric Hospitals.

The purpose of transplantation is to improve the health or save the life of the recipient. Although organ transplantation is a method generally accepted by society, there are still people who, referring to moral and ethical aspects, reject its validity. A great threat to transplantology is also the lack of knowledge of the society resulting from insufficient education.The aim of this study was to find out attitudes and opinions about organ transplantation and to determine the level of acceptance of organ and tissue transplantation.The tool chosen for the study was a survey questionnaire. The research group consisted of 200 people. Approval from the Bioethics Committee was obtained to conduct the study.The studies showed that more than half of the respondents (57%) would agree to organ donation for transplantation after the death of a loved one. Age was found to be statistically significant (P = .001). Older people showed more doubts about transplantation than people under 30. Over 80% of respondents agreed that initiatives to educate the public about transplantation are needed.The respondents refer to transplantation positively as a method of treating and saving life, and more than half of respondents would agree to donate their organs for transplant after the death of a loved one. The majority of respondents described their attitude toward transplantation as positive, admitting that the objection to donating is due to the ignorance and too little awareness on the subject. 

Attitudes Toward Organ Transplantation.

Mastoparan (MP) is an antimicrobial cationic tetradecapeptide with the primary structure INLKALAALAKKIL-NH2. This amphiphilic α-helical peptide was originally isolated from the venom of the wasp Paravespula lewisii. MP shows a variety of biological activities, such as inhibition of the growth of Gram-positive and Gram-negative bacteria, as well as hemolytic activity and activation of mast cell degranulation. Although MP appears to be toxic, studies have shown that its analogs have a potential therapeutic application as antimicrobial, antiviral and antitumor agents. In the present study we have designed and synthesized several new chimeric mastoparan analogs composed of MP and other biologically active peptides such as galanin, RNA III inhibiting peptide (RIP) or carrying benzimidazole derivatives attached to the ε-amino side group of Lys residue. Next, we compared their antimicrobial activity against three reference bacterial strains and conformational changes induced by membrane-mimic environments using circular dichroism (CD) spectroscopy. A comparative analysis of the relationship between the activity of peptides and the structure, as well as the calculated physicochemical parameters was also carried out. As a result of our structure–activity study, we have found two analogs of MP, MP-RIP and RIP-MP, with interesting properties. These two analogs exhibited a relatively high antibacterial activity against S. aureus compared to the other MP analogs, making them a potentially attractive target for further studies. Moreover, a comparative analysis of the relationship between peptide activity and structure, as well as the calculated physicochemical parameters, may provide information that may be useful in the design of new MP analogs.

/pdf/structure-activity-relationship-of-new-chimeric-analogs-of-2ht5bgz1.pdf

Katarzyna Wiśniewska

Papers

Peptidoglycan-associated lipoprotein (Pal) of Gram-negative bacteria: function, structure, role in pathogenesis and potential application in immunoprophylaxis.

Review of Best Practices for Patient Monitoring to Improve the Effectiveness of Therapy in Pediatric Hospitals.

Attitudes Toward Organ Transplantation.

Structure–Activity Relationship of New Chimeric Analogs of Mastoparan from the Wasp Venom Paravespula lewisii