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Microtubules are cytoskeletal structures involved in stability, transport andorganization in the cell. The building blocks, the a- and b-tubulin heterodimers, form protofilamentsthat associate laterally into the hollow microtubule. Microtubule also exists as highly stable doubletmicrotubules in the cilia where stability is needed for ciliary beating and function. The doubletmicrotubule maintains its stability through interactions at its inner and outer junctions where its A-and B-tubules meet. Here, using cryo-electron microscopy, bioinformatics and mass spectrometryof the doublets of Chlamydomonas reinhardtii and Tetrahymena thermophila, we identified twonew inner junction proteins, FAP276 and FAP106, and an inner junction-associated protein,FAP126, thus presenting the complete answer to the inner junction identity and localization. Ourstructural study of the doublets shows that the inner junction serves as an interaction hub thatinvolves tubulin post-translational modifications. These interactions contribute to the stability of thedoublet and hence, normal ciliary motility.

Antibiotic resistance is a major global health issue that has seen alarming rates of increase in all parts of the world over the past two decades. The surge in antibiotic resistance has resulted in longer hospital stays, higher medical costs, and elevated mortality rates. Constant attempts have been made to discover newer and more effective antimicrobials to reduce the severity of antibiotic resistance. Plant secondary metabolites, such as essential oils, have been the major focus due to their complexity and bioactive nature. However, the underlying mechanism of their antimicrobial effect remains largely unknown. Understanding the antimicrobial mode of action of essential oils is crucial in developing potential strategies for the use of essential oils in a clinical setting. Recent advances in genomics and proteomics have enhanced our understanding of the antimicrobial mode of action of essential oils. We might well be at the dawn of completing a mystery on how essential oils carry out their antimicrobial activities. Therefore, an overview of essential oils with regard to their antimicrobial activities and mode of action is discussed in this review. Recent approaches used in identifying the antimicrobial mode of action of essential oils, specifically from the perspective of genomics and proteomics, are also synthesized. Based on the information gathered from this review, we offer recommendations for future strategies and prospects for the study of essential oils and their function as antimicrobials.

Microtubules are cytoskeletal structures involved in stability, transport and organization in the cell. The building blocks, the a- and b-tubulin heterodimers, form protofilaments that associate laterally into the hollow microtubule. Microtubule also exists as highly stable doublet microtubules in the cilia where stability is needed for ciliary beating and function. The doublet microtubule maintains its stability through interactions at its inner and outer junctions where its A- and B-tubules meet. Here, using cryo-electron microscopy, bioinformatics and mass spectrometry of the doublets of Chlamydomonas reinhardtii and Tetrahymena thermophila, we identified two new inner junction proteins, FAP276 and FAP106, and an inner junction-associated protein, FAP126, thus presenting the complete answer to the inner junction identity and localization. Our structural study of the doublets shows that the inner junction serves as an interaction hub that involves tubulin post-translational modifications. These interactions contribute to the stability of the doublet and hence, normal ciliary motility., identifier:2050-084X

Misuse of antibiotics in the clinical and agricultural sectors has caused the emergence of multidrugresistant (MDR) Klebsiella pneumoniae which contributes a threat to human health. In this study, we assessed the feasibility of lavender essential oil (LVO) as an antimicrobial agent in combinatory therapy with meropenem in suppressing the growth of carbapenemase-producing K. pneumoniae (KPC-KP). Synergistic interactions between LVO and meropenem were detected, which signifcantly reduce the inhibitory concentration of both LVO and meropenem by 15 and 4-fold respectively. Comparative proteomic profling identifed a disruption in the bacterial membrane via oxidative stress that was indicated by loss of membrane and cytoplasmic proteins and the upregulation of oxidative regulators. As a proof of concept, zeta potential measurements showed a change in cell surface charge while outer membrane permeability measurement indicated an increase in membrane permeability following exposure to LVO. This was indicative of a disrupted outer membrane. Ethidium bromide infux/efux assays demonstrated no signifcant efux pump inhibition by LVO, and scanning electron microscopy revealed irregularities on the cell surface after exposure to LVO. Oxidative stress was also detected with increased level of ROS and lipid peroxidation in LVO-treated cells. In conclusion, our data suggest that LVO induced oxidative stress in K. pneumoniae which oxidizes the outer membrane, enabling the infux of generated ROS, LVO and meropenem into the bacterial cells, causing damage to the cells and eventually death.

Background: Clinacanthus nutans (CN) is a small shrub native to tropical Asia known for their anti-oxidant, anti-inflammation, anti-cancer, and anti-viral activities. Objectives: This study aimed to investigate the effect of CN extract on human embryonic kidney cell line (HEK-Blue™-4) in a proteomic perspective. Materials and Methods: Comparative proteomic profiling through two-dimensional sodium dodecyl sulfate gel electrophoresis was performed on HEK-Blue™-4 treated with CN leaf polar extract. Results: We successfully identified seven upregulated proteins, of which five promoted the growth of the HEK-Blue™-4 cells. Interestingly, a potent antioxidant enzyme which neutralizes reactive oxygen or nitrogen species, peroxiredoxin-1 was also upregulated in HEK-Blue™-4 cell lines after treatment with CN leaf polar extract. Conclusion: CN leaf polar extract promotes the growth of HEK-Blue™-4 cells and induced the expression of peroxiredoxin-1, which protects the cells from reactive oxygen species during the inflammation process.

Antimicrobials are useful compounds intended to eradicate or stop the growth of harmful microorganisms. The sustained increase in the rates of antimicrobial resistance (AMR) worldwide is worrying and poses a major public health threat. The development of new antimicrobial agents is one of the critical approaches to overcome AMR. However, in the race towards developing alternative approaches to combat AMR, it appears that the scientific community is falling behind when pitched against the evolutionary capacity of multi-drug resistant (MDR) bacteria. Although the “pioneering strategy” of discovering completely new drugs is a rational approach, the time and effort taken are considerable, the process of drug development could instead be expedited if efforts were concentrated on enhancing the efficacy of existing antimicrobials through: combination therapies; bacteriophage therapy; antimicrobial adjuvants therapy or the application of nanotechnology. This review will briefly detail the causes and mechanisms of AMR as background, and then provide insights into a novel, future emerging or evolving strategies that are currently being evaluated and which may be developed in the future to tackle the progression of AMR.

Carbapenemase-producing Klebsiella pneumoniae (KPC-KP) remains the most notorious nosocomial pathogen due to resistance towards all β-lactam antibiotics. Mining of novel antimicrobials, especially from essential oils are crucial to address this issue. Hence, this study was undertaken to identify and elucidate the mode of action of novel antimicrobial agents from essential oils. From the preliminary screening of five essential oils, lavender essential oil (LVO) reacted synergistically with meropenem, reducing the effective dosage of LVO from 10% to 0.63% and meropenem from 32 μg/mL to 8 μg/mL. The other four essential oils reacted additively with meropenem with cinnamon bark essential oil (CBO) having the highest degree of additivity, reducing the effective dosage of CBO from 0.16% to 0.08% and meropenem from 32 μg/mL to 16 μg/mL. Comparative proteomic analysis suggested membrane disruption, as indicated by reduced abundance of membrane and cytoplasmic proteins in LVO- and CBO-treated KPC-KP cells. Upregulation of oxidative stress regulator and downregulation of oxidative stress-sensitive proteins indicates presence of oxidative stress upon exposure to essential oil, explaining the membrane disruption phenomena via lipid peroxidation. Membrane disruption assays, namely zeta potential measurement, outer membrane permeability assay and scanning electron microscopy was performed to validate the membrane disruption speculation. It was observed that exposure to LVO and CBO increases the membrane zeta potential and membrane permeability of KPC-KP cells. Membrane disruption can also be seen in the scanning electron microscopy with corrugated bacterial surface. The results strongly suggest that LVO and CBO disrupt the bacterial membrane via induction of oxidative stress. Comparative studies between additive and synergistic interaction revealed that additivity interaction (CBO-meropenem) are slightly inferior when compared to the synergistic combinations (LVO-meropenem) in te

The evolution of antimicrobial resistance (AMR) in pathogens has prompted extensive research to find alternative therapeutics. Plants rich with natural secondary metabolites are one of the go-to reservoirs for discovery of potential resources to alleviate this problem. Terpenes and their derivatives comprising of hydrocarbons, are usually found in essential oils (EOs). They have been reported to have potent antimicrobial activity, exhibiting bacteriostatic and bactericidal effects against tested pathogens. This brief review discusses the activity of terpenes and derivatives against pathogenic bacteria, describing the potential of the activity against AMR followed by the possible mechanism exerted by each terpene class. Finally, ongoing research and possible improvisation to the usage of terpenes and terpenoids in therapeutic practice against AMR are discussed.

Klebsiella pneumoniae (KP) remains the most prevalent nosocomial pathogen and carries the carbapenemase (KPC) gene which confers resistance towards carbapenem. Thus, it is necessary to discover novel antimicrobials to address the issue of antimicrobial resistance in such pathogens. Natural products such as essential oils are a promising source due to their complex composition. Essential oils have been shown to be effective against pathogens, but the overall mechanisms have yet to be fully explained. Understanding the molecular mechanisms of essential oil towards KPC-KP cells would provide a deeper understanding of their potential use in clinical settings. Therefore, we aimed to investigate the mode of action of essential oil against KPC-KP cells from a proteomic perspective by comparing the overall proteome profile of KPC-KP cells treated with cinnamon bark (Cinnamomum verum J. Presl) essential oil (CBO) at their sub-inhibitory concentration of 0.08% (v/v). A total of 384 proteins were successfully identified from the non-treated cells, whereas only 242 proteins were identified from the CBO-treated cells. Proteins were then categorized based on their biological processes, cellular components and molecular function prior to pathway analysis. Pathway analysis showed that CBO induced oxidative stress in the KPC-KP cells as indicated by the abundance of oxidative stress regulator proteins such as glycyl radical cofactor, catalase peroxidase and DNA mismatch repair protein. Oxidative stress is likely to oxidize and disrupt the bacterial membrane as shown by the loss of major membrane proteins. Several genes selected for qRT-PCR analysis validated the proteomic profile and were congruent with the proteomic abundance profiles. In conclusion, KPC-KP cells exposed to CBO undergo oxidative stress that eventually disrupts the bacterial membrane possibly via interaction with the phospholipid bilayer. Interestingly, several pathways involved in the bacterial membrane repair syst

There are three common outcomes when testing the application of combinatory therapies for potential use in the clinical setting against multi-drug resistant (MDR) bacteria; whether synergistic, additive or antagonistic. Due to their relatively more favourable outcomes, antibiotics and adjuvant achieving synergism have been the primary focus in the development of therapeutics thus far; this has also resulted in less attention given to additive interactions, which may be equally effective. Hence, in this study, the authors investigated the effects of additivity using a representative combination model involving Cinnamomum verum (cinnamon bark) essential oil (CBO) and meropenem, a carbapenem class of antibiotics. Based on the zeta potential measurements, outer membrane permeability and scanning electron microscopy, synergistic and additive interactions of cinnamon bark oil (CBO) indicated comparable bacterial membrane disruption, alluding similar degrees of cell perturbations at the molecular level. Results from this study suggests that further investigations should be looked into for combinatorial therapeutic pairs achieving additive indices so as not to disqualify potentially useful alternatives in antibiotic therapy.

Antibiotic resistance had first been reported not long after the discovery of the first antibiotic and has remained a major public health issue ever since. Challenges are constantly encountered during the mitigation process of antibiotic resistance in the clinical setting; especially with the emergence of the formidable superbug, a bacteria with multiple resistance towards different antibiotics; this resulted in the term multidrug resistant (MDR) bacteria. This rapid evolution of the resistance phenomenon has propelled researchers to continuously uncover new antimicrobial agents in a bid to hopefully, downplay the rate of evolution despite a drying pipeline. Recently, there has been a paradigm shift in the mining of potential antimicrobials; in the past, targets for drug discovery were from microorganisms and at current, the focus has moved onto plants, this is mainly due to the beneficial attributes that plants are able to confer over that of microorganisms. This review will briefly discuss antibiotic resistance mechanisms employed by resistant bacteria followed by a detailed expository regarding the use of secondary metabolites from plants as a potential solution to the MDR pathogen. Finally, future prospects recommending enhancements to the usage of plant secondary metabolites to directly target antibiotic resistant pathogens will be discussed.