Biology subjects

Mora, M.

Publications and source records attributed to Mora, M..

8 recordsLinked to original sources

bioRxiv2026

Coordinated cell and chloroplast growth and its perturbation by chloroplast DNA replication inhibition in green algae

Coordination among cell growth, chloroplast expansion, and organelle genome dynamics is fundamental to algal physiology, yet its regulation remains unclear. We used time-resolved single-cell analyses to examine scaling relationships among cell size, chloroplast volume, nuclear dynamics, and nucleoid organization in Desmodesmus communis and Chlamydomonas reinhardtii under normal conditions and after inhibition of chloroplast DNA replication with nalidixic acid (NAL). Under control conditions, both species showed coordinated scaling among cell, chloroplast, and nuclear size, while nucleoid dynamics were driven mainly by changes in number. NAL disrupted these relationships in a species- and time-dependent manner. In C. reinhardtii, prolonged treatment uncoupled chloroplast and nuclear growth from cell expansion and led to fewer, enlarged nucleoids, consistent with impaired replication. In contrast, D. communis largely maintained coordinated scaling, with effects mainly limited to reduced nucleoid proliferation and delayed division. Temporal analyses indicated that NAL primarily affected nucleoid replication and segregation, with secondary consequences for chloroplast growth and cell-cycle progression. These findings identify chloroplast genome dynamics as a regulatory link between organelle growth and cell division.

cell biology↗

bioRxiv2020

Molecular fluctuations as a ruler of force-induced protein conformations

Molecular fluctuations directly reflect the underlying energy landscape. Variance analysis can probe protein dynamics in several biochemistry-driven approaches, yet measurement of probe-independent fluctuations in proteins exposed to mechanical forces remains only accessible through steered molecular dynamics simulations. Using single molecule magnetic tweezers, here we conduct variance analysis to show that individual unfolding and refolding transitions occurring in dynamic equilibrium in a single protein under force are hallmarked by a change in the protein's end-to-end fluctuations, revealing a change in protein stiffness. By unfolding and refolding three structurally distinct proteins under a wide range of constant forces, we demonstrate that the associated change in protein compliance to reach force-induced thermodynamically-stable states scales with the protein's contour length, in agreement with the sequence-independent FJC model of polymer physics. Our findings will help probe the conformational dynamics of proteins exposed to mechanical force at high resolution, of central importance in mechanosensing and mechanotransduction.

biophysics↗

bioRxiv2019

Genome-wide analysis of DNA uptake by naturally competent Haemophilus influenzae

The genomes of naturally competent Pasteurellaceae and Neisseriaceae have many short uptake sequences (USS), which allow them to distinguish self-DNA from foreign DNA. To fully characterize this preference we developed genome-wide maps of DNA uptake using both a sequence-based computational model and genomic DNA that had been sequenced after uptake by and recovery from competent Haemophilus influenzae cells. When DNA fragments were shorter than the average USS spacing of ~1000 bp, sharp peaks of uptake were centered at USS and separated by valleys with 1000-fold lower uptake. Long DNA fragments (1.5-17 kb) gave much less variation, with 90% of positions having uptake within two-fold of the mean. All detectable uptake biases arose from sequences that fit the USS uptake motif. Simulated competition predicted that, in its respiratory tract environment, H. influenzae will efficiently take up its own DNA even when human DNA is present in 100-fold excess.

microbiology↗

bioRxiv2019

Transactional sex among men who have sex with men participating in the CohMSM prospective cohort study in West Africa

Men who have sex with men (MSM) are at much greater risk of HIV infection in Africa. Little is known about their involvement in transactional sex (TS). We aimed to characterize MSM reporting TS (MSM-TS) and to identify factors associated with their sexual practices using data from the prospective cohort study CohMSM conducted in Burkina Faso, Cote dIvoire, Mali and Togo. Our study focused on HIV-negative MSM, recruited between 06/2015 and 01/2018 by a team of trained peer educators. Scheduled study visits at 6, 12 and 18 months included medical examinations, HIV screening, risk-reduction counselling and face-to-face interviews to collect information on their sociodemographic characteristics, sexual behaviours, and HIV risk-reduction strategies. Three stigmatization sub-scores were constructed. The generalized estimating equation method was used for data analysis. Of the 630 HIV-negative participants recruited at baseline, 463, 410 and 244 had a follow-up visit at 6- and 12- and 18-months, respectively. Over a total of 1747 visits, 478 TS encounters were reported by 289 MSM-TS (45.9%). Of the latter, 91 participants reported systematic TS (31.5%), 55 (19.0 %) stopped reporting TS after baseline, and 53 (18.3%) reported TS after baseline. Ninety participants (31.1 %) reported occasional TS. After adjusting for country of study and follow-up visits, the following factors, reported for the previous 6 months, were associated with a greater likelihood of TS: younger age, an educational level <high-school diploma, satisfaction with current sex life, group sex with men, multiple male sexual partners, condomless anal sex, receptive or versatile anal sex with male sexual partners, giving benefits in exchange for sex with a man, alcohol consumption and drug use during sex, and experiencing stigmatization. The majority of MSM in this study who received benefits in exchange for sex had high-risk HIV infection exposure practices and were characterized by socioeconomic difficulties.

epidemiology↗

bioRxiv2019

Male clients of male sex workers in West Africa: A neglected high risk population

Research on male clients of male sex workers (MCMSW) has been neglected for a long time globally. We aimed to characterize MCMSW and to identify factors associated with their sexual practices using data from the prospective cohort study CohMSM conducted in Burkina Faso, Cote dIvoire, Mali and Togo. Our study focused on HIV-negative men who have sex with other men (MSM) recruited between 06/2015 and 01/2018 by a team of trained peer educators. Scheduled study visits at 6, 12 and 18 months included medical examinations, HIV screening, risk-reduction counselling and face-to-face interviews to collect information on their sociodemographic characteristics, sexual behaviours, and HIV risk-reduction strategies (HIV-RRS). Three stigmatization sub-scores were constructed (experienced, perceived and internalized). Mixed-effects logistic regression was used for data analysis. Of the 280 participants recruited at baseline, 238, 211 and 118, respectively, had a follow-up visit at 6, 12 and 18 months. Over a total of 847 visits, 47 transactional sex (TS) encounters were reported by 38 MCMSW (13.6%). Of the latter, only one participant reported systematic TS (2.6%), 18 (47.4 %) stopped reporting TS after baseline, and 6 (15.8%) reported TS after baseline. Thirteen participants (34.2 %) reported occasional TS. After adjusting for country of study and age, the following self-reported factors were associated with a greater likelihood of being MCMSW: protected anal sex, exclusively insertive anal sex with male sexual partners, avoidance of sex after consuming psychoactive products and experiencing stigmatization (all during the previous 6 months). The majority of MCMSW in this study employed HIV-RRS with male sexual partners, including engaging in protected anal sex, avoidance of sex when consuming psychoactive products, and practising exclusively insertive anal sex.

epidemiology↗

bioRxiv2019

The International Space Station selects for microorganisms adapted to the extreme environment, but does not induce genomic and physiological changes relevant for human health

The International Space Station (ISS) is a unique, completely confined habitat for the human crew and co-inhabiting microorganisms. Here, we report on the results of the ISS experiment "EXTREMOPHILES". We aimed to exploit the microbial information obtained from three surface and air sampling events aboard the International Space Station during increments 51 and 52 (2017) with respect to: i) microbial sources, diversity and distribution within the ISS, ii) functional capacity of microbiome and microbial isolates, iii) extremotolerance and antibiotics-resistance (compared to ground controls), and iv) microbial behavior towards ISS-relevant materials such as biofilm formation, or potential for degradation. We used wipe samples and analyzed them by amplicon and metagenomics sequencing, cultivation, comparative physiological studies, antibiotic resistance tests, genome analysis of isolates and co-incubation experiments with ISS-relevant materials. The major findings were: i) the ISS microbiome profile is highly similar to ground-based confined indoor environments, ii) the ISS microbiome is subject to fluctuations and indicative for the (functional) location, although a core microbiome was present over time and independent from location, iii) the ISS selects for microorganisms adapted to the extreme environment, but does not necessarily induce genomic and physiological changes which might be relevant for human health, iv) cleanrooms and cargo seems to be a minor source of microbial contamination aboard, and v) microorganisms can attach to and grow on ISS-relevant materials. Biofilm formation might be a threat for spacecraft materials with the potential to induce instrument malfunctioning with consequences for mission success. We conclude that our data do not raise direct reason for concern with respect to crew health, but indicate a potential threat towards biofilm formation and material integrity in moist areas.

microbiology↗

bioRxiv2018

Dead or Alive? Molecular life-dead distinction in human stool samples reveals significantly different composition of the microbial community

The gut microbiome is strongly interwoven with human health. Conventional gut microbiome analysis generally involves 16S rRNA gene targeting next generation sequencing (NGS) of stool microbial communities, and correlation of results with clinical parameters. However, some microorganisms may not be alive at the time of sampling, and thus their impact on the human health is potentially less significant. As conventional NGS methods do not differentiate between viable and dead microbial components, retrieved results provide only limited information.\n\nPropidium monoazide (PMA) is frequently used in food safety monitoring and other disciplines to discriminate living from dead cells. PMA binds to free DNA and masks it for subsequent procedures. In this article we show the impact of PMA on the results of 16S rRNA gene-targeting NGS from human stool samples and validate the optimal applicable concentration to achieve a reliable detection of the living microbial communities.\n\nFresh stool samples were treated with a concentration series of zero to 300 M PMA, and were subsequently subjected to amplicon-based NGS. The results indicate that a substantial proportion of the human microbial community is not intact at the time of sampling. PMA treatment significantly reduced the diversity and richness of the sample depending on the concentration and impacted the relative abundance of certain important microorganisms (e.g. Akkermansia, Bacteroides). Overall, we found that a concentration of 100 M PMA was sufficient to quench signals from disrupted microbial cells.\n\nThe optimized protocol proposed here can be easily implemented in classical microbiome analyses, and helps to retrieve an improved and less blurry picture of the microbial community composition by excluding signals from background DNA.

microbiology↗

bioRxiv2018

Exosomes and exosomal miRNAs from muscle-derived fibroblasts promote skeletal muscle fibrosis

We investigated in vitro and in vivo the pro-fibrotic role of exosomes released by muscle-derived fibroblasts of Duchenne muscular dystrophy (DMD) patients, and of miRNAs carried by exosomes. We found that exosomes from DMD fibroblasts, but not from myoblasts, had significantly higher levels of miR-199a-5p, a miRNA up-regulated in fibrotic conditions, compared to control exosomes. In control fibroblasts, exposure to DMD fibroblast-derived exosomes induced a myofibroblastic phenotype with increase in -smooth actin, collagen and fibronectin transcript and protein expression, soluble collagen production and deposition, cell proliferation, and activation of Akt and ERK signalling, while exposure to control exosomes did not. These findings were related to transfer of high levels of miR-199a-5p and to reduction of its target caveolin-1. Finally, injection of DMD fibroblast-derived exosomes into mouse tibialis anterior muscle after cardiotoxin-induced necrosis, produced greater fibrosis than control exosomes.\n\nOur findings indicate that exosomes produced by local fibroblasts in the DMD muscle are able to induce phenotypic conversion of normal fibroblasts to myofibroblasts thereby increasing the fibrotic response; and suggest miR-199a-5p and caveolin-1as potential therapeutic targets.

pathology↗