Aravind Ayyolath

To maintain the integrity of the outer membrane of Gram-negative bacteria, such as Escherichia coli, the levels of two essential components, phospholipids (PL) and lipopolysaccharide (LPS), are tightly regulated, although the underlying molecular mechanisms are unclear. E. coli synthesizes three main PLs, including essential phosphatidylethanolamine and phosphatidylglycerol and nonessential cardiolipin (CL). We showed that CL synthesis is conditionally essential in ΔlapD bacteria. Using this synthetic lethal phenotype, we isolated suppressors that rescued growth at elevated temperatures. We showed that loss-of-function mutations in cdsA encoding CDP-diglyceride synthetase, and pgsA, which encodes phosphatidylglycerophosphate synthase, bypass this lethality. Such mutations reduce the relative abundance of acidic phospholipids, which are otherwise elevated in Δ(lapD clsA) bacteria, and increase the amounts of cis-vaccenic acid without altering amounts of LpxC mediating the first committed step in LPS biosynthesis. Interestingly, overexpression of genes, including accC and glnB, whose products can inhibit fatty acid/PL synthesis, overcame the lethality of Δ(lapD clsA) bacteria. We demonstrated that PgsA co-purifies with LapB, which regulates LpxC stability and acts as a hub for proteins involved in PL and LPS biosynthesis, including LapD. Overall, our results reveal that LapD is positioned at the regulatory nexus between LPS assembly and fatty acid/PL synthesis.

Lipopolysaccharide (LPS) is an essential component of the outer membrane (OM) of Gram-negative bacteria, and its levels are tightly co-regulated with phospholipid (PL) amounts. This homeostatic regulation necessitates the involvement of numerous genes, including lapD in a poorly defined manner. To understand the function of LapD, we took advantage of the synthetic lethal phenotype conferred by the concomitant absence of LapD and myristoyltransferase LpxM or heptosyltransferase WaaC and isolated extragenic suppressors that could bypass this lethality. Suppressor analyses of Δ(lapD lpxM) bacteria identified five single amino acid exchanges in AccA and two in each of AccC and AccD. These proteins comprise different subunits of the acetyl-CoA carboxylase complex, which catalyzes the rate-limiting step in the initiation of fatty acid synthesis, mediating the conversion of acetyl-CoA to malonyl-CoA. Fatty acid analysis revealed that these mutations restored the ratio of saturated to unsaturated fatty acids and repressed elevated PL levels. Suppressor analyses of Δ(lapD waaC) identified a single amino acid substitution in LptD, which is required for LPS assembly in the OM, and in NlpI, which regulates the amount of peptidoglycan hydrolase MepS. These results posit LapD as the point of critical regulation of homeostatic control of three essential cell envelope components.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder caused due to the damage and loss of neurons in specific brain regions. It is the most common form of dementia observed in older people. The symptoms start with memory loss and gradually cause the inability to speak and do day-to-day activities. The cost of caring for those affected individuals is huge and is probably beyond most developing countries capability. Current pharmacotherapy for AD includes compounds that aim to increase neurotransmitters at nerve endings. This can be achieved by cholinergic neurotransmission through inhibition of the cholinesterase enzyme. The current research aims to find natural substances that can be used as drugs to treat AD. The present work identifies and explains compounds with considerable Acetylcholinesterase (AChE) inhibitory activities. The pigment was extracted from the Penicillium mallochii ARA1 () strain using ethyl acetate, and the active compound was identified using chromatographic techniques followed by structural confirmation with NMR. AChE inhibition experiments, enzyme kinetics, and molecular dynamics simulation studies were done to explain the pharmacological and pharmacodynamic properties. We identified that the compound sclerotiorin in the pigment has AChE inhibitory activity. The compound is stable and can bind to the enzyme non-competitively. Sclerotiorin obeys all the drug-likeliness parameters and can be developed as a promising drug in treating AD.

Alzheimer’s disease (AD), also called senile dementia is a neurodegenerative disease seen commonly in the elderly and is characterised by the formation of β-amyloid plaques and neurofibrillary tangles (NFT). Though a complete understanding of the disease is lacking, recent studies showed the role of the enzyme acetylcholinesterase (AChE) in pathogenesis. Finding new lead compounds from natural sources has always been a quest for researchers. Endophytic fungi are a set of microbes that reside within plants without causing any harm. This study focuses on screening endophytes for the production of active acetylcholinesterase inhibitors. Five endophytic fungi were isolated from Catharanthus roseus and screened for AChE inhibitory activity. Three isolates were found to inhibit AChE inhibitory activity and were distinguished based on molecular and microscopic methods. The mycelial extract was taken for the bioassay-guided column chromatography and TLC was performed on the active fraction. The GC–MS and NMR analysis identified the active compounds in the extract as 9-hexadecen-1-ol and erucamide. Molecular docking studies revealed that the compounds are thermodynamically feasible and have significant glide scores. Computational studies revealed that the hydroxyl group of 9-hexadecen-1-ol forms a hydrogen bond with Ser 293 in the active site of AChE, whereas the active site interactions were predominantly hydrophobic in the case of erucamide and are reflected in AChE inhibition assays.

Recently, the demand for fungal pigments has increased due to their several benefits over synthetic dyes. Many species of fungi are known to produce pigments and a large number of fungal strains for pigment production are yet to be extensively investigated. The natural pigment from sustainable natural sources has good economic and industrial value. Many synthetic colorants used in textile and various industries have many harmful effects on the human population and environment. Pigments and coloring agents may be extracted from a wide range of fungal species. These compounds are among the natural compounds having the most significant promise for medicinal, culinary, cosmetics, and textile applications. This study attempts to isolate and optimize the fermentation conditions of Penicillium sclerotiorum strain AK‐1 for pigment production. A dark yellow‐colored pigment was isolated from the strain with significant extractive value and antioxidant capacity. This study also identifies that the pigment does not have any cytotoxic effect and is multicomponent. The pigment production was optimized for the parameters such as pH, temperature, carbon and nitrogen source. Fabric dyeing experiments showed significant dyeing capacity of the pigment on cotton fabrics. Accordingly, the natural dye isolated from P. sclerotiorum strain AK‐1 has a high potential for industrial‐scale dyeing of cotton materials.

Trypsin is a protein‐digesting enzyme that is essential for the growth and regeneration of bone, muscle, cartilage, skin, and blood. The trypsin inhibitors have various role in diseases such as inflammation, Alzheimer's disease, pancreatitis, rheumatoid arthritis, cancer prognosis, metastasis and so forth. From 10 endophytic fungi isolated, we were able to screen only one strain with the required activity. The fungus with activity was obtained as an endophyte from Dendrophthoe falcata and was later identified as Nigrospora sphaerica. The activity was checked by enzyme assays using trypsin. The fungus was fermented and the metabolites were extracted and further purified by bioassay‐guided chromatographic methods and the compound isolated was identified using gas chromatography–mass spectrometry. The compound was identified as quercetin. Docking studies were employed to study the interaction. The absorption, distribution, metabolism, and excretion analysis showed satisfactory results and the compound has no AMES and hepatotoxicity. This study reveals the ability of N. sphaerica to produce bioactive compound quercetin has been identified as a potential candidate for trypsin inhibition. The present communication describes the first report claiming that N. sphaerica strain AVA‐1 can produce quercetin and it can be considered as a sustainable source of trypsin active‐site inhibitors.

Coronavirus disease 2019 (COVID-19), a highly contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has drastically changed the lifestyle of people around the globe. Due to the lack of specific and effective antiviral drugs, transmission of the disease increases exponentially and makes it more serious and harder to control. Drugs that were assumed to be effective against COVID-19 have failed in various stages of clinical trials and this made the scientific community more disappointed. But, the race of researchers for developing new and effective antiviral to stop the disease progression still continues and our work is one among them. This study is an attempt to analyze the action of Tectoquinone and Acteoside; an important phytocompound, on SARS-CoV2 viral protease via in silico approach. The compounds were selected on the basis of their molecular docking values and they were subjected to molecular dynamics simulations about 50 ns to determine the stability and the thermodynamic feasibility between the target and the ligands. Binding energies like hydrogen bonding, hydrophobic and electrostatic interactions of the complexes were determined after MD simulations. The Pharmacokinetics and drug likeness evaluation of the compounds provide a strong evidence for the use of these compounds in developing drugs for clinical trials. Thus, the current study reveals the potential phytoconstituents present in Tectona grandis Linn to inhibit COVID-19 viral protease and thereby act as a lead therapeutic agent. Communicated by Ramaswamy H. Sarma