Biology subjects

Lemos, M.

Publications and source records attributed to Lemos, M..

6 recordsLinked to original sources

bioRxiv2025

Variations in cow milk and teat skin microbiota across the lactation cycle with intra-mammary cephalosporin use at dry-off

Cephalosporins and other broad-spectrum antibiotics are frequently administered prophylactically into the udder when dairy cows end their lactation cycle, termed dry-off, to reduce mastitis risk. However, the use of antibiotics on cows that do not have signs of infection may result in the selection of microbes resistant to antibiotics and negatively alter the udder microbiome composition. In this study, the effects of intramammary cephalosporin therapy with either Cephapirin (CB) or Ceftiofur (CH) on milk and teat skin microbiota were examined for three dairies in California. Bacterial composition was measured for cows with low somatic cell counts (SCC,<100,000 cells /mL) and high, subclinical SCC (>200,000 cells/mL). Samples were collected at dry-off (before treatment), seven days later, and 55-75 Days in Milk (DIM) in the next lactation cycle. The milk and skin microbiota were largely separated based on dairy (milk: R2 = 6.22, skin: R2 = 7.56) and day of sampling (milk: R2 = 4.74 and skin: R2 = 3.77). CB or CH use was associated with a small but significant impact on the milk microbiota beta-diversity (Bray-Curtis, p =0.003, R2= 1.4%) but no effect was observed on the skin. At one dairy (Dairy 3), milk from cows receiving CB and CH had a reduction in proportions of Staphylococcaceae at 55-75DIM compared to untreated cows. Overall, antibiotic use did not result in large significant changes to bacterial diversity in milk or on the teat skin, and instead the microbiota at those sites mainly differed between the time and location of sampling. ImportanceThe use of antibiotics in agriculture is under increasing scrutiny due to the rising spread of antimicrobial resistant bacteria. Our study showed that common preventative antibiotic intramammary treatment of cows with cephalosporins at the end their lactation (dry-off) had minimal effects on the milk and teat skin microbiota on asymptomatic cows with high somatic cell counts.

microbiology↗

bioRxiv2022

ACE2 nanoparticles prevent cell entry of SARS-CoV-2

The continual evolution of SARS-CoV-2 has challenged the efficacy of many COVID19 vaccines and treatment options. One strategy that evades viral escape is using the entry receptor, human Angiotensin-Converting Enzyme 2 (hACE2). Soluble hACE2 receptor domains show potential as decoys but genetic modifications are necessary to provide sufficient efficacy. However, these engineered constructs are potentially susceptible to viral escape. We combined native hACE2 with viral vectors to form nanoparticles presenting hACE2 analogous to human cells. Cell-based viral infection assays and cryogenic in-situ tomography show that hACE2 nanoparticles sequester viruses through aggregation, efficiently blocking entry of SARS-CoV-2 and its variants in model cell systems and human respiratory tract explants using native hACE2. Thus, we show that hACE2 nanoparticles have high potential as pan-variant COVID19 therapeutics.

cell biology↗

bioRxiv2021

A plastidial retrograde-signal potentiates biosynthesis of systemic stress response activators

O_LIPlants employ an array of intricate and hierarchical signaling cascades to perceive and transduce informational cues to synchronize and tailor adaptive responses. Systemic stress response (SSR) is a recognized complex signaling and response network quintessential to plants local and distal responses to environmental triggers, however, the identity of the initiating signals has remained fragmented. C_LIO_LIHere, we show that both biotic (aphids and viral pathogens) and abiotic (high-light and wounding) stresses induce accumulation of the plastidial-retrograde-signaling metabolite, methylerythritol cyclodiphosphate (MEcPP), leading to reduction of the phytohormone, auxin, and the subsequent decreased expression of the phosphatase, PP2C.D1. C_LIO_LIThis enables phosphorylation of mitogen-activated protein kinases (MAPK3/6), and the consequential induction of the downstream events ultimately resulting in biosynthesis of the two SSR priming metabolites, pipecolic- and N-hydroxy-pipecolic acid. C_LIO_LIThis work identifies plastids as the initiation site, and the plastidial retrograde-signal, MEcPP as the initiator of a multi-component signaling cascade potentiating the biosynthesis of SSR activators, in response to biotic and abiotic triggers. C_LI

plant biology↗

bioRxiv2019

Timing and original features of flagellum assembly in trypanosomes during development in the tsetse fly

Trypanosoma brucei exhibits a complex life cycle alternating between tsetse flies and mammalian hosts. When parasites infect the fly, cells differentiate to adapt to life in various tissues, which is accompanied by drastic morphological and biochemical modifications especially in the proventriculus. This key step represents a bottleneck for salivary gland infection. Here we monitored flagellum assembly in trypanosomes during differentiation from the trypomastigote to the epimastigote stage, i.e. when the nucleus migrates to the posterior end of the cell. Three-dimensional electron microscopy (Focused Ion Bean Scanning Electron Microscopy, FIB-SEM) and immunofluorescence assays provided structural and molecular evidence that the new flagellum is assembled while the nucleus migrates towards the posterior region of the body. Two major differences with well known procyclic cells are reported. First, growth of the new flagellum begins when the associated basal body is found in a posterior position relative to the mature one. Second, the new flagellum acquires its own flagellar pocket before rotating on the left side of the anterior-posterior axis. FIB-SEM revealed the presence of a structure connecting the new and mature flagellum and serial sectioning confirmed morphological similarities with the flagella connector of procyclic cells. We discuss potential function of the flagella connector in trypanosomes from the proventriculus. These findings show that T. brucei finely modulates its cytoskeletal components to generate highly variable morphologies.\n\nAuthor SummaryTrypanosoma brucei is a flagellated parasitic protist that causes human African trypanosomiasis, or sleeping sickness and that is transmitted by the bite of tsetse flies. The complex life cycle of T. brucei inside the tsetse digestive tract requires adaptation to specific organs and follow a strictly defined order. It is marked by morphological modifications in cell shape and size, as well organelle positioning. In the proventriculus of tsetse flies, T. brucei undergoes a unique asymmetric division leading to two very different daughter cells: one with a short and one with a long flagellum. This organelle is crucial for the trypanosome life cycle as it is involved in motility, adhesion and morphogenesis. Here we investigated flagellum assembly using molecular and 3D Electron Microscopy approaches revealing that flagellum construction in proventricular trypanosomes is concomitant with parasite differentiation. During flagellum growth, the new flagellum is connected to the mature one and rotates around the mature one after its emergence at the cell surface. The sequence of events is different from what is observed in the well-studied procyclic stage in culture revealing different processes governing morphological development. These results highlight the importance to study pathogen development in their natural environment.

microbiology↗

bioRxiv2018

Bidirectional intraflagellar transport is restricted to only two microtubule doublets in the trypanosome flagellum

Intraflagellar transport (IFT) is the rapid bidirectional movement of large protein complexes driven by kinesin and dynein motors along microtubule doublets of cilia and flagella. Here we used a combination of high-resolution electron and light microscopy to investigate how and where these IFT trains move within the flagellum of the protist Trypanosoma brucei. Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) analysis of trypanosomes showed that trains are found almost exclusively along two sets of doublets (3-4 and 7-8) and distribute in two categories according to their length. High-resolution live imaging of cells expressing mNeonGreen::IFT81 or GFP::IFT52 revealed for the first time IFT trafficking on two parallel lines within the flagellum. Anterograde and retrograde IFT occur on each of these lines. At the distal end, a large individual anterograde IFT train is converted in several smaller retrograde trains in the space of 3-4 seconds while remaining on the same side of the axoneme.

cell biology↗

bioRxiv2018

Biallelic Mutations in LRRC56 encoding a protein associated with intraflagellar transport, cause mucociliary clearance and laterality defects

Defective motile cilia are responsible for a group of heterogeneous genetic conditions characterised by dysfunction of the apparatus responsible for generating fluid flows. Primary ciliary dyskinesia (PCD) is the prototype for such disorders and presents with impaired pulmonary mucus clearance, susceptibility to chronic recurrent respiratory infections, male infertility and laterality defects in about 50 % of patients. Here we report biallelic variants in LRRC56 (also known as ODA8), identified in two unrelated consanguineous families. The phenotype comprises laterality defects and chronic pulmonary infections. High speed video microscopy of cultured patient epithelial cells showed severely dyskinetic cilia, but no obvious ultra-structural abnormalities on routine transmission electron microscopy (TEM). Further investigation revealed that LRRC56 interacts with the intraflagellar transport (IFT) protein IFT88. The link to IFT was interrogated in Trypanosoma brucei. In this protist, LRRC56 is recruited to the cilium during axoneme construction, where it co-localises with IFT trains and facilitates the addition of dynein arms to the distal end of the flagellum. In T. brucei carrying LRRC56 null mutations, or a mutation (p.Leu259Pro) corresponding to the p.Leu140Pro variant seen in one of the affected families, we observed abnormal ciliary beat patterns and an absence of outer dynein arms restricted to the distal portion of the axoneme. Together, our findings confirm that deleterious variants in LRRC56 result in a human disease, and suggest this protein has a likely role in dynein transport during cilia assembly that is evolutionarily important for cilia motility.

genetics↗