Biology subjects

Ilic, S.

Publications and source records attributed to Ilic, S..

7 recordsLinked to original sources

bioRxiv2024

Rodent Gut Bacteria Coexisting with an Insect Gut Virus in Parasitic Cysts: Metagenomic Evidence of Microbial Translocation and Co-adaptation in Spatially-Confined Niches

In medicine, parasitic cysts or cysticerci (fluid-filled cysts, larval stage of tapeworms) are believed to be sterile (no bacteria), and therein, the treatment of cysticerci infestations of deep extra-intestinal tissues (e.g., brain) relies almost exclusively on the use of antiparasitic medications, and rarely antibiotics. To date, however, it is unclear why common post-treatment complications include abscessation. This study quantified the microbial composition of parasitic cyst contents in a higher-order rodent host, using multi-kingdom shotgun metagenomics, to improve our understanding of gut microbial translocation and adaptation strategies in wild environments. Analysis was conducted on DNA from two hepatic parasitic cysts (Hydatigera (Taeenia) taeniaeformis) in an adult vole mouse (Microtus arvalis), and from feces, liver, and peritoneal fluid of three other vole family members living in a vegetable garden in Ohio, USA. Bacterial metagenomics revealed the presence of gut commensal/opportunistic species, including Parabacteroides distasonis, Klebsiella variicola, Enterococcus faecium, and Lactobacillus acidophilus, inhabiting the cysts. Parabacteroides distasonis and other species were also present outside the cyst in the peritoneal fluid. Remarkably, viral metagenomics revealed various murine viral species, but unexpectedly, it detected an insect-origin virus from the army moth (Pseudaletia/Mythimna unipuncta) known as Mythimna unipuncta granulovirus A (MyunGV-A) in both cysts, and in one fecal and one peritoneal sample from two different voles, indicating survival of the insect virus and adaption in voles. Metagenomics also revealed a significantly lower probability of fungal detection in the cysts compared to other samples (peritoneal fluid, p<0.05; and feces p<0.05), with single taxon detection in each cyst for Malassezia and Pseudophaeomoniella oleicola. The samples with a higher probability of fungi were the peritoneal fluid. In conclusion, commensal/pathobiont bacterial species can inhabit parasitic tapeworm cysts, which needs to be considered during therapeutic decisions of cysticerci or other chronic disease scenarios where immune privileged and spatially restricted ecosystems with limited nutrients and minimal presence of immune cells could facilitate microbial adaptation, such as within gut wall cavitating micropathologies in Crohns disease.

microbiology↗

bioRxiv2020

Cell-penetrating peptide conjugates of indole-3-acetic acid-based DNA primase/Gyrase inhibitors as potent antitubercular agents against planktonic and biofilm culture of Mycobacterium smegmatis

Mycobacterium tuberculosis (Mtb) is a pathogenic bacterium that caused 1.5 million fatalities globally in 2018. New strains of Mtb resistant to all known classes of antibiotics pose a global healthcare problem. In this work we have conjugated novel indole-3-acetic acid-based DNA primase/gyrase inhibitor with cell-penetrating peptide via cleavable and non-cleavable bonds. For non-cleavable linkage, inhibitor was conjugated with peptide via an amide bond to the N-terminus, whereas a cleavable linkage was obtained by conjugating the inhibitor through a disulfide bond. We performed the conjugation of the inhibitor either directly on a solid surface, or by using solution-phase chemistry. M. smegmatis (non-pathogenic model of Mtb) was used to determine the minimal inhibitory concentration (MIC) of the synthetic conjugates. Conjugates were found more active as compared to free inhibitor molecules. Strikingly, the conjugate also impair the development of biofilm, showing a therapeutic potential against infections caused by both planktonic and sessile forms of mycobacterium species.

microbiology↗

bioRxiv2020

Reconfiguring Okazaki fragment start sites on a genome by using a data driven approach

DNA-protein interactions are essential in all aspects of every living cell. Understanding of how features embedded in the DNA sequence affect specific interactions with proteins is challenging but important, since it may contribute to finding the means to regulate metabolic pathways involving DNA-protein interactions. Using a massive experimental benchmark dataset of binding scores for DNA sequences and a machine learning workflow, we describe the binding to DNA of T7 primase, as a model system for specific DNA-protein interactions. Effective binding of T7 primase to its specific DNA recognition sequences triggers the formation of RNA primers that serve as Okazaki fragment start sites during DNA replication.

biochemistry↗

bioRxiv2019

Understanding artificial mouse-microbiome heterogeneity and six actionable themes to increase study power

The negative effects of data clustering due to (intra-class/spatial) correlations are well-known in statistics to interfere with interpretation and study power. Therefore, it is unclear why housing many laboratory mice ([≥]4), instead of one-or-two per cage, with the improper use/reporting of clustered-data statistics, abound in the literature. Among other sources of artificial confounding, including cyclical oscillations of the cage microbiome, we quantified the heterogeneity of modern husbandry practices/perceptions. The objective was to identify actionable themes to re-launch emerging protocols and intuitive statistical strategies to increase study power. Amenable for interventions, cost-vs-science discordance was a major aspect explaining heterogeneity and the reluctance to change. Combined, four sources of information (scoping-reviews, professional-surveys, expert-opinion, and implementability-score-statistics) indicate that a six-actionable-theme framework could minimize artificial heterogeneity. With a Housing Density Cost Simulator in Excel and fully annotated statistical examples, this framework could reignite the use of study power to monitor the success/reproducibility of mouse-microbiome studies.

scientific communication and education↗

bioRxiv2019

SIRT6 is a DNA double-strand break sensor

DNA double strand breaks are the most deleterious type of DNA damage. In this work, we show that SIRT6 directly recognizes DNA damage through a tunnel-like structure, with high affinity for double strand breaks. It relocates to sites of damage independently of signalling and known sensors and activates downstream signalling cascades for double strand break repair by triggering ATM recruitment, H2AX phosphorylation and the recruitment of proteins of the Homologous Recombination and Non-Homologous End Joining pathways. Our findings indicate that SIRT6 plays a previously uncharacterized role as DNA damage sensor, which is critical for initiating the DNA damage response (DDR). Moreover, other Sirtuins share some DSB binding capacity and DDR activation. SIRT6 activates the DDR, before the repair pathway is chosen, and prevents genomic instability. Our findings place SIRT6 at the top of the DDR and pave the road to dissect the contributions of distinct double strand break sensors in downstream signalling.

biochemistry↗

bioRxiv2019

Synthetic Dual-Acting Small-Molecule Inhibitors That Target Mycobacterial DNA Replication

Mycobacterium tuberculosis (Mtb) is a pathogenic bacterium and a causative agent of tuberculosis (TB), a disease that kills more than 1.5 million people worldwide annually. One of the main reasons for this high mortality rate is the evolution of new Mtb strains that are resistant to available antibiotics. Therefore, new therapeutics for TB are in constant demand. Here we report the development of such inhibitors that target two DNA replication enzymes of Mtb, namely DnaG primase and DNA gyrase, which share a conserved TOPRIM fold near the inhibitors binding site. The molecules were developed on the basis of previously reported inhibitors for T7 DNA primase that bind near the TOPRIM fold. In order to improve the physicochemical properties of the molecules as well as their inhibitory effect on primase and gyrase, 49 novel compounds were synthesized as potential drug candidates in three stages of optimization. The last stage of chemical optimization yielded two novel inhibitors for the fast-growing nonpathogenic model Mycobacterium smegmatis (Msmg).

biochemistry↗

bioRxiv2018

DNA sequence context controls the binding and processivity of T7 DNA primase

Primases are key enzymes involved in DNA replication. They act on single-stranded DNA, and catalyze the synthesis of short RNA primers used by DNA polymerases. Here, we investigate the DNA-binding and activity of the bacteriophage T7 primase using a new workflow called High-Throughput Primase Profiling (HTPP). Using a unique combination of high-throughput binding assays and biochemical analyses, HTPP reveals a complex landscape of binding specificity and functional activity for the T7 primase, determined by sequences flanking the primase recognition site. We identified specific features, such as G/T-rich flanks, which increase primase-DNA binding up to 10-fold and, surprisingly, also increase the length of newly formed RNA (up to 3-fold). To our knowledge, variability in primer length has not been reported for this primase. We expect that applying HTPP to additional enzymes will reveal new insights into the effects of DNA sequence composition on the DNA recognition and functional activity of primases.

biophysics↗