Search

Gut microbiota is a master regulator of host physiology. Intestinal microbes produce numerous metabolites through primary and secondary metabolic pathways, and many of which are dependent on host diet. The effects exerted by these microbial-derived metabolites represent the combined output of host-microbes interactions, which influence host energy metabolism, development and function of the immune system, maintenance of mucosal integrity, as well as intestinal microbiota community dynamics. In this chapter, we provide an overview of the methodologies used in metabolomic studies to dissect and understand host-microbiota interactions. Furthermore, we discuss the current knowledge on specific microbial-derived metabolites, notably secondary bile acids, short chain fatty acids, and tryptophan metabolites and their role in affecting host health.

Introduction: Irritable Bowel Syndrome (IBS) is a gastrointestinal (GI) disorder that exhibits different GI and neurological symptoms such as abdominal pain, diarrhoea, constipation and mood disorders. The gut microbiota play an important role in modulating the communication between the Central Nervous System (CNS) and the GI tract, the so-called microbiota-gut-brain axis. In this context, IBS is a clear example of the alteration of the fine equilibrium between the gut microbiota and the CNS. Furthermore it has been observed that probiotic treatments of IBS results in the relief of GI and neurological symptoms, thus we could hypothesize the direct impact of the gut microbiota on IBS physiopathology. Since the IBS bacterial gut microbiota has been extensively studied we focused our attention also on the fungal counterpart of the gut microbiota, "the mycobiota". Methods and aims. The aim of the present work was to evaluate biodiversity in bacterial and fungal microbiota of a cohort of 20 IBS subject and 21 healthy subject (HS) through culture-based and metagenomics approaches. The bacterial diversity that relies on DNA polymorphism has been performed by means of cluster analysis of ARDRA profiles. Moreover the absolute abundances of bifidobacteria and enterobacteria has been evaluated by qPCR. For IBS gut mycobiota characterization, fungal strains from IBS stool samples were isolated and identified by mean of ITS1-4 sequencing. Furthermore, isolates were phenotypically characterized to evaluate their resistance to GI tract stresses (temperature, low pH and oxbile resistance), while Candida isolates were further clustered by means of their RAPD profiles. Results: The cluster analysis of ARDRA profiles showed that IBS bacterial microbiota clusters apart from HS microbiota. In addition we observed a 2.8-fold increase in the absolute abundance of enterobacteria in IBS subjects vs HS. The analysis of the gut mycobiota revealed significant differences in fungal isolates abundance in IBS subjects vs HS even if we did not find any significant difference in species richness. In particular, results showed an abundance of fungi (61.8% C. albicans), with a higher number of colony count 4.7 log10 CFU/g faeces in IBS subjects respect to HS faecal samples with 1.9 log10 CFU/g (48,75% C. albicans). RAPD prolfile analysis of C. albicans and C. parapsilosis showed that IBS isolates clustered apart from HS isolates, suggesting their different genotypical background. Finally, we observed that IBS fungal isolates showed different phenotypical features with an increased ability to growth to high temperatures and low pH respect to isolates from HS. Conclusions: Our results showed the presence of alterations in the microbial community structure of IBS subjects, both at bacterial and fungal level. The absolute abundance of enterobacteria in IBS subjects suggests their connection with putative inflammatory phenomena as previously observed in IBS and other pathologies (Lee and Park, 2014). The phenotypical characterization of IBS fungal isolates revealed that such isolates showed a different response in respect GI-like stresses. Moreover we observed that C. albicans and C. parapsilosis isolates from IBS are both phenotypically and genotypically different from HS Candida isolates suggesting their putative different ecological distribution. Finally we could hypotesize that dysbiosis of the gut microbiota in IBS could be one of the driving factor in IBS pathophysiology that could be responsible of intestinal fungal population overgrowth. Lee JY, Park KS. 2014. World J Gastroenterol 20:2456-2469

Irritable Bowel Syndrome (IBS) is a psychosomatic gastrointestinal disorder which aetiology is not well clear, although several factors indicate the involvement of the gut microbiota, remarking the importance of the microbiota-gut-brain axis in IBS pathophysiology. We therefore characterized the gut microbiota in a cohort of 20 IBS subjects and 21 healthy subjects (HS) focusing also on the characterization of the fungal gut microbiota.

During the last 25 years of activity, the Physical Oceanography Research Group, previously known as the PO-Unit, and currently established within the Department of Geosciences of the University of Malta, has been promoting the downscaling of broad scope marine core services to higher resolution local scale domains for the Maltese Islands. Several services are delivered either by an intrinsic data elaboration or by making use of and integrating the COPERNICUS Marine Environment Monitoring Service (CMEMS) data to local marine data streams. Local observations are also integrated with higher resolution forecasts for the preparation and provision of dedicated services that address real specific needs of sub-regional and coastal users. This effort has yielded valuable climatological datasets covering the Maltese coastal waters and spanning over several years. This work focusses on the climatologies derived from numerical models and satellites, and compiled within the Interreg MED programme AMAre (Actions for Marine Protected Areas) project., peer-reviewed

The human gut microbiota directly affect human health. Alterations in the composition of commensal bacteria can lead to chronic inflammation also predisposing individuals to fungal infections. Commensal fungi are important in human health and changes in commensal fungal populations have been shown to deeply affect pathologies not directly related to fungi, such as Inflammatory Bowel Diseases. Rett syndrome (RTT) is a neurodegenerative disorder caused by a mutation in MECP2. High proportion of RTT subjects suffer of gastrointestinal disorders, implying a link between RTT and the gut microbiota. We studied the bacterial and fungal gut microbiota of patients affected by RTT by a multilevel approach to understand whether changes in gut microbiota of RTT patients could be associated with GI abnormalities, inflammatory status and cytokine dysregulation previously observed. Our findings revealed that RTT patients harbor a distinct and less diverse bacterial and fungal microbiota compared to healthy subjects in which Bifidobacterium and Candida are the most abundant genera. The immunological responses exerted by RTT yeast isolates in our in vitro cell model suggest that fungi could contribute to the gastrointestinal abnormalities and intestinal inflammation observed in our RTT study cohort.

Rett syndrome (RTT) is a neurodegenerative disorder caused by a mutation in MECP2. To date, the mechanism that trigger the disease have yet to be explained. Gut microbiome controls CNS activities through endocrine, metabolic and immune pathways and yeast infections shift IDO’s activity leading to a reduction of kineurenine that act as a neuroprotective agent. In addition, kineurenine is affected by the immune system, dysfunction of which has been implicated in the etiology of ASD. The hypothesis we want to test is if alterations in microbiota-mediated immunomodulation are reflected in alterations in microbiota-mediated neuromodulation. We characterized the gut microbiome/mycobiome of RTT patients through culture based and metagenomics approaches. Stool sample from 50 RTT patient and 30 HS have been collected. DNA has been extracted and submitted to metagenomic analysis in order to analyze bacterial and fungal communities’ structure. We discovered C. albicans as significantly more represented in heathy controls with respect to RTT patients. On the contrary, the highly emerging potentially invasive species, Trichosporon spp. and S. cerevisiae have been isolated solely in RTT patients.