Salgueiro, V. | Search bioRxiv

bioRxiv2023

Maintenance of cell wall remodeling and vesicle production are connected in Mycobacterium tuberculosis

Pathogenic and nonpathogenic mycobacteria secrete extracellular vesicles (EVs) under various conditions. EVs produced by Mycobacterium tuberculosis (Mtb) have raised significant interest for their potential in cell communication, nutrient acquisition, and immune evasion. However, the relevance of vesicle secretion during tuberculosis infection remains unknown due to the limited understanding of mycobacterial vesicle biogenesis. We have previously shown that a transposon mutant in the LCP-related gene virR (virRmut) manifested a strong attenuated phenotype during experimental macrophage and murine infections, concomitant to enhanced vesicle release. In this study, we aimed to understand the role of VirR in the vesicle production process in Mtb. We employ genetic, transcriptional, proteomics, ultrastructural and biochemical methods to investigate the underlying processes explaining the enhanced vesiculogenesis phenomenon observed in the virRmut. Our results establish that VirR is critical to sustain proper cell permeability via regulation of cell envelope remodeling possibly through the interaction with similar cell envelope proteins, which control the link between peptidoglycan and arabinogalactan. These findings advance our understanding of mycobacterial extracellular vesicle biogenesis and suggest that these set of proteins could be attractive targets for therapeutic intervention.

microbiology↗

bioRxiv2019

Carnivore endozoochory of a dry fruited tree can benefit quarry passive restoration

As more work assert passive restoration as a complementary approach to technical reclamation, it is imperative to know its drivers. Although the consequences of endozoochory are crucial to predict passive restoration success, few experimental studies assess the use of heavily disturbed sites by seed dispersers such as carnivores and how the seeds they bring in emerge and survive. Using an indoor sowing experiment conducted in situ, we examined for the first time how carnivore endozoochorous seeds collected in a quarry potentially influence its passive restoration, through effects on plant emergence and survival. Also, we tested whether sowing date and water soaking, relevant factors when sowings are to be carried out, would affect seedling emergence and survival rates when compared with the effect of endozoochory. Most interesting in our analysis were the results for Carob tree (Ceratonia siliqua), a dry-fruited species being used in an ongoing action of artificial revegetation of this quarry located within a natural park in Portugal. Irrespective of the carnivore species, endozoochorous carob seeds collected in the quarry performed similarly to untreated seeds regarding emergence rates. Endozoochorous carob seedlings showed greater mortality rates but the net result for the plant can still be the colonization of recently vacant habitats by a large proportion of viable seeds. The later carob seeds were sown, the faster seedlings emerged, including endozoochorous seedlings. As expected, water soaking implied faster emergences. Broadly, plantings, sowings with previous soaking, and carnivore-mediated seed dispersal of this dry-fruited tree can jointly enhance quarry restoration. Implications for practiceO_LIRestorers can undertake pilot sowing experiments similar to ours prior to large scale revegetation campaigns to identify which species can benefit the most from endozoochory. C_LIO_LICarnivores in the surroundings of a quarry contribute a large proportion of viable seeds, likely assisting quarry passive restoration. C_LIO_LICarnivores ingesting carob seeds later in the fruiting season may assist quarry passive revegetation more readily as seeds ingested around that time emerge earlier. C_LIO_LIImmersion in tap water seems to be a simple, inexpensive, and a highly efficient method to break physical dormancy when carob seed sowings are to be carried out in degraded sites. C_LI

ecology↗