Biology subjects

Ligoxygakis, P.

Publications and source records attributed to Ligoxygakis, P..

10 recordsLinked to original sources

bioRxiv2023

Analysis of the influence of peptidoglycan turnover and recycling on host-pathogen interaction in the Gram-positive pathogen Staphylococcus aureus

During peptidoglycan recycling (PR) bacteria can recover extracellular fragments of peptidoglycan (PGN) liberated by peptidoglycan turnover (PT) during cell growth and division, and reuse them in cell wall biosynthesis or central carbon metabolism. In Gram-negative bacteria, PR has been well studied, and functions in the induction of resistance to certain classes of antibiotics, and in host-pathogen interaction. However, while Gram-negative cell envelope architecture allows for highly efficient PR, Gram-positive bacteria, which lack an outer cell membrane and are instead enclosed by a glycopolymer layer, can shed large quantities of PGN-derived material to the external environment during growth. Nonetheless, the occurrence of PR was recently demonstrated in several Gram-positive bacteria, including the Gram-positive bacterial pathogen Staphylococcus aureus, and its potential adaptive functions are largely unexplored. Given the known roles of PR in Gram-negative bacteria, and that Gram-positive bacteria include several important human pathogens, we asked what role PR may play during Gram-positive pathogen-host interaction. Usingthe model insect host Drosophila melanogaster, we demonstrate that S. aureus mutants impaired in extracellular PGN hydrolysis ({Delta}atl) and PGN fragment uptake ({Delta}murP) show differential virulence compared to their wild-type counterpart. This was linked to increased activation of the D. melanogaster Toll-cascade by spent supernatant from the {Delta}atl mutant. Thus, we propose that S. aureus, and potentially other Gram-positive bacteria, may use extracellular PGN degradation during PT to simultaneously process PGN fragments for recycling and for immune evasion, while recovery and/or metabolism of peptidoglycan fragments during PR may play more subtle roles in determining virulence. Author summaryPGN is a key component of the bacterial cell wall, forming a stress-bearing sacculus surrounding the cell and providing cell shape. During growth and division, the sacculus is dynamically degraded and remodelled to ensure daughter cell separation, resulting in PT. PGN fragments released during PT can be recovered and reutilised by the cell during PR. In Gram-negative pathogens, PR is linked to antibiotic resistance, virulence and modulation of host immune recognition. In Gram-positive bacteria, PR was only recently observed. Here, we explore the roles of PT and PR in host-pathogen interaction in S. aureus, a Gram-positive pathogen of significant clinical relevance. Disruption of PT in S. aureus affected host-pathogen interaction through altering host recognition of shed PGN fragments and PR through modulation of PGN fragment recovery. This improves our understanding of the biology of this important pathogen and may aid development of novel therapeutic approaches to treat S. aureus infections.

microbiology↗

bioRxiv2022

Sex-specific deubiquitylation drives immune-related neurodegeneration in Drosophila

Risk of neurodegenerative disease such as late onset Alzheimers is linked to aberrant ubiquitinylation and accumulation of non-degraded proteins in brain cells. A glial network of innate immune genes modulates inflammatory responses to such protein deposition. However, vulnerability differs between the sexes. Here, we show that the Drosophila homologue of the deubiquitylase Trabid can align the sex-specific aspects of neurodegenerative phenotypes with changes in ubiquitylation and inflammatory activity. An enzymatically null Trabid in flies, caused sex-specific changes in locomotion, sleep patterns, brain histology and ultimately, lifespan. These changes were underscored by altered ubiquitin and proteome enrichment profiles and the same enzymatic activity as its human counterpart. When the sex-determination gene transformer was silenced in astrocytes or immunocompetent tissues, sex differences were significantly reduced. Our results indicate that Trabid underscores sex-specificity in disease neurology, by controlling the balance between ubiquitylation and inflammation.

immunology↗

bioRxiv2020

HYD3, a conidial hydrophobin of the fungal entomopathogen Metarhizium acridum induces the immunity of its specialist host locust

Conidial hydrophobins in fungal pathogens of plants1,2, insects3,4, and humans5,6 are required for fungal attachment and are associated with high virulence. They are believed to contribute to the pathogenesis of infection by preventing immune recognition5,6. Here, we refute this generalisation offering a more nuanced analysis. We show that MacHYD3, a hydrophobin located on the conidial surface of the specialist entomopathogenic fungus Metarhizium acridum, activates specifically the humoral and cellular immunity of its own host insect, Locusta migratoria manilensis (Meyen) but not that of other non-host insects. When topically applied to the cuticle, purified MacHYD3 improved the resistance of locusts to both specialist and generalist fungal pathogens but had no effect on the fungal resistance of other insects, including Spodoptera frugiperda and Galleria mellonella. Hydrophobins extracted from the generalist fungal pathogens M. anisopliae and Beauveria bassiana had no effect on the resistance of locusts to fungal infection. Thus, the host locust has evolved to recognize the conidial hydrophobin of its specialist fungal pathogen, whereas conidial hydrophobins from generalist fungi are able to evade recognition. Our results distinguish the immunogenic potential of conidial hydrophobins between specialist and generalist fungi.

microbiology↗

bioRxiv2020

From pathogen to commensal to probiotic: modification of Microbacterium nematophilum-C. elegans interaction during chronic infection by the absence of host insulin signalling

The nematode worm Caenorhabditis elegans depends on microbes in decaying vegetation as its food source. To survive in an environment rich in opportunistic pathogens, C. elegans has evolved an epithelial defence system where surface-exposed tissues such as epidermis, pharynx, intestine, vulva and hindgut have the capacity of eliciting appropriate immune defences to acute gut infection. However, it is unclear how the worm responds to chronic intestinal infections. To this end, we have surveyed C. elegans mutants that are involved in inflammation, immunity and longevity to find their phenotypes during chronic infection. Worms that grew in a monoculture of the natural pathogen Microbacterium nematophilum (CBX102 strain) had a reduced lifespan and health span. This was independent of intestinal colonisation as both CBX102 and the derived avirulent strain UV336 were early persistent colonisers. In contrast, long-lived daf-2 mutants were resistant to chronic infection, showing reduced colonisation and a higher age-dependent vigour. In fact, UV336 acted as a probiotic in daf-2, showing a lifespan extension beyond OP50, the E. coli strain used for laboratory C. elegans culture. Longevity and vigour of daf-2 mutants growing on CBX102 was dependent on the FOXO orthologue DAF-16. Since the DAF-2/DAF-16 axis is present in most metazoans this suggests an evolutionary conserved host mechanism to modify a pathogen to a commensal.

immunology↗

bioRxiv2020

Tools for the genetic manipulation of Herpetomonas muscarum

microbiology↗

bioRxiv2019

The Phlebotomus papatasi transcriptomic response to trypanosomatid-contaminated blood is robust but non-specific

Leishmaniasis, caused by parasites of the genus Leishmania, is a disease that effects up to 8 million people worldwide. Parasites are transmitted to human and animal hosts through the bite of an infected sand fly. Novel strategies for disease control, require a better understanding of the key step for transmission namely, the establishment of infection inside the fly. In this work we wanted to identify fly transcriptomic signatures associated with infection success or failure. We used next generation sequencing to describe the transcriptome of the sand fly Phlebotomus papatasi when fed with blood alone or with blood containing one of three trypanosomatids: Leishmania major, Leishmania donovani and Herpetomonas muscarum: a parasite not transmitted to humans. Of these, only L. major was able to successfully establish an infection in P. papatasi. However, the transcriptional signatures observed were not specific to success or failure of infection but a generalised response to the blood meal. This implies that sand flies perceive Leishmania as just a feature of their microbiome landscape and that any strategy to tackle transmission should focus on the response towards the blood meal rather than parasite establishment. Authors summaryLeishmania are parasites that cause leishmaniasis, a group of serious diseases that affect millions of people, mainly across the subtropics and tropics. They are transmitted to humans by phlebotomine sand flies. However, despite establishment in the insects midgut being key to transmission, early infection events inside the insect are still unclear. Here, we study the gene expression response of the insect vector to a Leishmania parasite that is able to establish infection (L. major) one that is unable to do so (L. donovani) as well as one that is not a natural parasite of sand flies (Herpetomonas muscarum). We found that responses following any of the infected blood meals was very similar to uninfected blood meal. However, changes post-blood meal from day 1 to day 9 were dramatic. As a blood feeding insect can accumulate three times its weight in one blood meal, this seems to be the most important physiological change rather than the presence of the parasite. The latter might be just one in a number of microbes the insect encounters. This result will generate new thinking around the concept of stopping transmission by controlling the parasite inside the insect.

immunology↗

bioRxiv2019

Transcriptional and genomic parallels between the monoxenous parasite Herpetomonas muscarum and Leishmania

Trypanosomatid parasites are causative agents of important human and animal diseases such as sleeping sickness and leishmaniasis. Most trypanosomatids are transmitted to their mammalian hosts by insects, often belonging to Diptera (or true flies). These are called dixenous trypanosomatids since they infect two different hosts, in contrast to those that infect just insects (monoxenous). However, it is still unclear whether dixenous and monoxenous trypanosomatids interact similarly with their insect host, as fly-monoxenous trypanosomatid interaction systems are rarely reported and under-studied - despite being common in nature. Here we present the genome of monoxenous trypanosomatid Herpetomonas muscarum and discuss its transcriptome during in vitro culture and during infection of its natural insect host Drosophila melanogaster. The H. muscarum genome is broadly syntenic with that of human parasite Leishmania major. We also found strong similarities between the H. muscarum transcriptome during fruit fly infection, and those of Leishmania during sand fly infections. Overall this suggests Drosophila-Herpetomonas is a suitable model for less accessible insect-trypanosomatid host-parasite systems such as sand fly-Leishmania.\n\nAuthor SummaryTrypanosomes and Leishmania are parasites that cause serious Neglected Tropical Diseases (NTDs) in the worlds poorest people. Both of these are dixenous trypanosomatids, transmitted to humans and other mammals by biting flies. They are called dixenous as they can establish infections in two different types of hosts - insect vectors and mammals. In contrast, monoxenous trypanosomatids usually only infect insects. Despite establishment in the insects midgut being key to transmission of NTDs, events during early establishment inside the insect are still unclear in both dixenous and monoxenous parasites. Here, we study the interaction between a model insect - the fruit fly Drosophila melanogaster - and its natural monoxenous trypanosomatid parasite Herpetomonas muscarum. We show that both the genome of this parasite, and gene regulation at early stages of infection have strong parallels with Leishmania. This work has begun to identify evolutionarily conserved aspects of the process by which trypanosomatids establish in insects, thus potentially highlighting key checkpoints necessary for transmission of dixenous parasites. In turn, this might inform new strategies to control trypanosomatid NTDs.

microbiology↗

bioRxiv2018

Intestinal NF-κB and STAT signalling is important for uptake and clearance in a Drosophila-Herpetomonas interaction model.

Dipteran insects transmit diseases to humans, often in the form of trypanosomatid parasites. To accelerate research in more difficult contexts of dipteran-parasite relationships, we studied the interaction of the model dipteran Drosophila melanogaster and its natural trypanosomatid Herpetomonas muscarum. Parasite infection reduced fecundity but not lifespan in NF-{kappa}B/Relish-deficient flies. Gene expression analysis implicated the two NF-{kappa}B pathways Toll and Imd as well as STAT signalling. Tissue specific knockdown of key components of these pathways in enterocytes (ECs) and intestinal progenitor cells influenced initial numbers, infection dynamics and time of clearance. Herpetomonas triggered STAT activation and proliferation of Intestinal Stem Cells (ISCs). Loss of Relish suppressed the latter, resulting in increased parasite numbers and delayed clearance. Finally, loss of Toll signalling decreased EC numbers and enabled parasite persistence. This network of signalling may represent a general mechanism of the dipteran early response to trypanosomatids, crucial for parasite establishment and therefore transmission.\n\nAUTHOR SUMMARYNeglected Tropical Diseases are the most common diseases of the worlds poorest people. Many are caused by parasites called trypanosomatids that are transmitted to humans via insects belonging to the order of Diptera (also known as true flies). These flies (including tsetse, sand flies and black flies) are difficult to study in the lab and so the prospect of rapid progress in the basic biology of fly-parasite interaction is bleak. However, a model dipteran species with an extensive \"tool-box\" is the fruit fly Drosophila melanogaster with its natural trypanosomatid Herpetomonas muscarum. Here we establish the framework of their early interaction with the view that part of this interaction will represent an evolutionary conserved component of the dipteran response to parasite infection and will inform more targeted studies into medically important but difficult to study Diptera.

immunology↗

bioRxiv2018

A host-pathogen interaction screen identifies ada2 as a mediator of Candida glabrata defences against reactive oxygen species

Candida glabrata (C. glabrata) forms part of the normal human gut microbiota but can cause life-threatening invasive infections in immune-compromised individuals. C. glabrata displays high resistance to common azole antifungals, which necessitates new treatments. In this investigation, we identified five C. glabrata deletion mutants ({Delta}ada2, {Delta}bas1, {Delta}hir3,{Delta} ino2 and{Delta} met31) from a library of 196 transcription factor mutants that were unable to grow and activate an immune response in Drosophila larvae. This highlighted the importance of these transcription factors in C. glabrata infectivity. Further ex vivo investigation into these mutants revealed the requirement of C. glabrata ADA2 for oxidative stress tolerance. We confirmed this observation in vivo whereby growth of the C. glabrata {Delta}ada2 strain was permitted only in flies with suppressed production of reactive oxygen species (ROS). Conversely, overexpression of ADA2 promoted C. glabrata replication in infected wild type larvae resulting in larval killing. We propose that ADA2 orchestrates the response of C. glabrata against ROS-mediated immune defences during infection. With the need to find alternative antifungal treatment for C. glabrata infections, genes required for survival in the host environment, such as ADA2, provide promising potential targets.

microbiology↗

bioRxiv2018

Drosophila Toll links systemic immunity to long-term intestinal epithelial integrity

The intestine is an organ where immune and metabolic functions are co-ordinated with tissue renewal via progenitor somatic stem cells (PSSCs). How this is achieved is still unclear. We report that in Drosophila, a generalised infection increased PSSC numbers. This was mimicked by expressing a constitutive form of the immune receptor Toll in PSSCs and blocked when Toll was silenced via RNAi. Without infection, absence of bacterial recognition and downstream Toll signalling resulted in a short lifespan and an age-dependent decrease of PSSCs and gut microbiota. The latter implied a metabolic environment incompatible with the presence of bacteria. Indeed, infection or constitutive Toll signalling in PSSCs triggered 4E-BP transcription in enterocytes, while loss of signalling reduced it. 4E-BP controlled fat levels and sustained the microbiota suggesting that Toll-dependent regulation of 4E-BP was important for long-term gut function. Therefore, the Toll pathway is crucial for responses to both infection and microbiota.

immunology↗