Strategies and advancements in human microbiome description and the importance of culturomics

Gut microbiome research: Revealing the pathological mechanisms and treatment strategies of type 2 diabetes

The high prevalence and disability rate of type 2 diabetes (T2D) caused a huge social burden to the world. Currently, new mechanisms and therapeutic approaches that may affect this disease are being sought. With in-depth research on the pathogenesis of T2D and growing advances in microbiome sequencing technology, the association between T2D and gut microbiota has been confirmed. The gut microbiota participates in the regulation of inflammation, intestinal permeability, short-chain fatty acid metabolism, branched-chain amino acid metabolism and bile acid metabolism, thereby affecting host glucose and lipid metabolism. Interventions focusing on the gut microbiota are gaining traction as a promising approach to T2D management. For example, dietary intervention, prebiotics and probiotics, faecal microbiota transplant and phage therapy. Meticulous experimental design and choice of analytical methods are crucial for obtaining accurate and meaningful results from microbiome studies. How to design gut microbiome research in T2D and choose different machine learning methods for data analysis are extremely critical to achieve personalized precision medicine.

Dielectrophoresis for Isolating Low-Abundance Bacteria Obscured by Impurities in Environmental Samples

Bacterial communities associated with living organisms play critical roles in maintaining health and ecological balance. While dominant bacteria have been widely studied, understanding the role of low-abundance bacteria has become increasingly important due to their unique roles, such as regulating bacterial community dynamics and supporting host-specific functions. However, detecting these bacteria remains challenging, as impurities in environmental samples mask signals and compromise the accuracy of analyses. This study explored the use of dielectrophoresis (DEP) as a practical approach to isolate low-abundance bacteria obscured by impurities, comparing its utility to conventional centrifugation methods. Using two shrimp species, Neocaridina denticulata and Penaeus japonicus, DEP effectively isolated bacterial fractions while reducing impurities, enabling the detection of bacteria undetected in centrifuged samples. These newly detected bacteria were potentially linked to diverse ecological and host-specific functions, such as nutrient cycling and immune modulation, highlighting DEP as a highly potential approach to support the study of host-microbial interactions. Overall, we believe that DEP offers a practical solution for detecting overlooked bacteria in conventional methods and exploring their diversity and functional roles, with potential contributions to aquaculture and environmental biotechnology.

Culturable Human Microorganisms and the Impact of Transportation Conditions on Cultivability

The composition of the human microbiome is a critical health indicator, and culture-independent methodologies have substantially advanced our understanding of human-associated microorganisms. However, precise identification and characterization of microbial strains require culture-based techniques. Recently, the resurgence of culturomics, combined with high-throughput sequencing technology, has reduced the high labor demand of pure culture methods, facilitating a more efficient and comprehensive acquisition of culturable microbial strains. This study employed an integrated approach combining culturomic and high-throughput sequencing to identify culturable microorganisms on the human scalp and in human saliva and feces. Several Staphylococcus strains were identified from the scalp, whereas anaerobic microorganisms were dominant in the saliva and fecal samples. Additionally, the study highlighted the beneficial effects of transportation conditions (liquid nitrogen treatment, dry ice transport, and dimethyl sulfoxide [DMSO] buffer) in preserving culturable microorganisms. A robust methodology was developed for the large-scale acquisition of culturable microorganisms with optimized transport conditions that enhance the potential for isolating a greater diversity of culturable strains.

Lung microbiome: new insights into bronchiectasis' outcome

The present treatments for bronchiectasis, which is defined by pathological dilatation of the airways, are confined to symptom relief and minimizing exacerbations. The condition is becoming more common worldwide. Since the disease's pathophysiology is not entirely well understood, developing novel treatments is critically important. The interplay of chronic infection, inflammation, and compromised mucociliary clearance, which results in structural alterations and the emergence of new infection, is most likely responsible for the progression of bronchiectasis. Other than treating bronchiectasis caused by cystic fibrosis, there are no approved treatments. Understanding the involvement of the microbiome in this disease is crucial, the microbiome is defined as the collective genetic material of all bacteria in an environment. In clinical practice, bacteria in the lungs have been studied using cultures; however, in recent years, researchers use next-generation sequencing methods, such as 16S rRNA sequencing. Although the microbiome in bronchiectasis has not been entirely investigated, what is known about it suggests that Haemophilus, Pseudomonas and Streptococcus dominate the lung bacterial ecosystems, they present significant intraindividual stability and interindividual heterogeneity. Pseudomonas and Haemophilus-dominated microbiomes have been linked to more severe diseases and frequent exacerbations, however additional research is required to fully comprehend the role of microbiome in the evolution of bronchiectasis. This review discusses recent findings on the lung microbiota and its association with bronchiectasis.

A Simplified Label-Free Method for Proteotyping Sets of Six Isolates in a Single Liquid Chromatography-High-Resolution Tandem Mass Spectrometry Analysis

Clinical diagnostics and microbiology require high-throughput identification of microorganisms. Sample multiplexing prior to detection is an attractive means to reduce analysis costs and time-to-result. Recent studies have demonstrated the discriminative power of tandem mass spectrometry-based proteotyping. This technology can rapidly identify the most likely taxonomical position of any microorganism, even uncharacterized organisms. Here, we present a simplified label-free multiplexing method to proteotype isolates by tandem mass spectrometry that can identify six microorganisms in a single 20 min analytical run. The strategy involves the production of peptide fractions with distinct hydrophobicity profiles using spin column fractionation. Assemblages of different fractions can then be analyzed using mass spectrometry. Results are subsequently interpreted based on the hydrophobic characteristics of the peptides detected, which make it possible to link each taxon identified to the initial sample. The methodology was tested on 32 distinct sets of six organisms including several worst-scenario assemblages-with differences in sample quantities or the presence of the same organisms in multiple fractions-and proved to be robust. These results pave the way for the deployment of tandem mass spectrometry-based proteotyping in microbiology laboratories.

Culturing the unculturables: strategies, challenges, and opportunities for gut microbiome study

Metagenome sequencing techniques revolutionized the field of gut microbiome study. However, it is equipped with experimental and computational biases, which affect the downstream analysis results. Also, live microbial strains are needed for a better understanding of host-microbial crosstalks and for designing next-generation treatment therapies based on probiotic strains and postbiotic molecules. Conventional culturing methodologies are insufficient to get the dark gut matter on the plate; therefore, there is an urgent need to propose novel culturing methods that can fill the limitations of metagenomics. The current work aims to provide a consolidated evaluation of the available methods for host-microbe interaction with an emphasis on in vitro culturing of gut microbes using organoids, gut on a chip, and gut bioreactor. Further, the knowledge of microbial crosstalk in the gut helps us to identify core microbiota, and key metabolites that will aid in designing culturing media and co-culturing systems for gut microbiome study. After the deeper mining of the current culturing methods, we recommend that 3D-printed intestinal cells in a multistage continuous flow reactor equipped with an extended organoid system might be a good practical choice for gut microbiota-based studies.

An initial genomic blueprint of the healthy human oesophageal microbiome

Background

The oesophageal microbiome is thought to contribute to the pathogenesis of oesophageal cancer. However, investigations using culture and molecular barcodes have provided only a low-resolution view of this important microbial community. We therefore explored the potential of culturomics and metagenomic binning to generate a catalogue of reference genomes from the healthy human oesophageal microbiome, alongside a comparison set from saliva.

Results

Twenty-two distinct colonial morphotypes from healthy oesophageal samples were genome-sequenced. These fell into twelve species clusters, eleven of which represented previously defined species. Two isolates belonged to a novel species, which we have named Rothia gullae. We performed metagenomic binning of reads generated from UK samples from this study alongside reads generated from Australian samples in a recent study. Metagenomic binning generated 136 medium or high-quality metagenome-assembled genomes (MAGs). MAGs were assigned to 56 species clusters, eight representing novel Candidatus species, which we have named Ca. Granulicatella gullae, Ca. Streptococcus gullae, Ca. Nanosynbacter quadramensis, Ca. Nanosynbacter gullae, Ca. Nanosynbacter colneyensis, Ca. Nanosynbacter norwichensis, Ca. Nanosynococcus oralis and Ca. Haemophilus gullae. Five of these novel species belong to the recently described phylum Patescibacteria . Although members of the Patescibacteria are known to inhabit the oral cavity, this is the first report of their presence in the oesophagus. Eighteen of the metagenomic species were, until recently, identified only by hard-to-remember alphanumeric placeholder designations. Here we illustrate the utility of a set of recently published arbitrary Latinate species names in providing user-friendly taxonomic labels for microbiome analyses.Our non-redundant species catalogue contained 63 species derived from cultured isolates or MAGs. Mapping revealed that these species account for around half of the sequences in the oesophageal and saliva metagenomes. Although no species was present in all oesophageal samples, 60 species occurred in at least one oesophageal metagenome from either study, with 50 identified in both cohorts.

Conclusions

Recovery of genomes and discovery of new species represents an important step forward in our understanding of the oesophageal microbiome. The genes and genomes that we have released into the public domain will provide a base line for future comparative, mechanistic and intervention studies.

Culturomics, a potential approach paving the way toward bacteriotherapy

The human microbiota has been extensively studied over the past decade to describe its role in health and diseases. Numerous studies showed the presence of bacterial imbalance in a variety of human health conditions, suggesting great potential for the development of bacteriotherapies. Identifying mechanisms involving the human microbiota has been very challenging due to the complex data generated by molecular approaches and the limited number of organisms isolated by culture and described. This review summarizes the efforts done to describe the human microbiota through culturomics and the advancements in culturing the organisms residing at different body sites.

"Bacterial Consortium": A Potential Evolution of Fecal Microbiota Transplantation for the Treatment of Clostridioides difficile Infection

Fecal microbiota transplantation (FMT) consists of infusion of feces from a donor to a recipient patient in order to restore the resident microbial population. FMT has shown to be a valid clinical option for Clostridioides difficile infections (CDI). However, this approach shows several criticalities, such as the recruiting and screening of voluntary donors. Our aim was to evaluate the therapeutic efficacy of a synthetic bacterial suspension defined "Bacterial Consortium" (BC) infused in the colon of CDI patients. The suspension was composed by 13 microbial species isolated by culturomics protocols from healthy donors' feces. The efficacy of the treatment was assessed both clinically and by metagenomics typing. Fecal samples of the recipient patients were collected before and after infusion. DNA samples obtained from feces at different time points (preinfusion, 7, 15, 30, and 90 days after infusion) were analyzed by next-generation sequencing. Before infusion, patient 1 showed an intestinal microbiota dominated by the phylum Bacteroidetes. Seven days after the infusion, Bacteroidetes decreased, followed by an implementation of Firmicutes and Verrucomicrobia. Patient 2, before infusion, showed a strong abundance of Proteobacteria and a significant deficiency of Bacteroidetes and Verrucomicrobia. Seven days after infusion, Proteobacteria strongly decreased, while Bacteroidetes and Verrucomicrobia increased. Metagenomics data revealed an "awakening" by microbial species absent or low concentrated at time T0 and present after the infusion. In conclusion, the infusion of selected bacteria would act as a trigger factor for "bacterial repopulation" representing an innovative treatment in patients with Clostridioides difficile infections.

Culturing and Molecular Approaches for Identifying Microbiota Taxa Impacting Children's Obesogenic Phenotypes Related to Xenobiotic Dietary Exposure

Integrated data from molecular and improved culturomics studies might offer holistic insights on gut microbiome dysbiosis triggered by xenobiotics, such as obesity and metabolic disorders. Bisphenol A (BPA), a dietary xenobiotic obesogen, was chosen for a directed culturing approach using microbiota specimens from 46 children with obesity and normal-weight profiles. In parallel, a complementary molecular analysis was carried out to estimate the BPA metabolising capacities. Firstly, catalogues of 237 BPA directed-cultured microorganisms were isolated using five selected media and several BPA treatments and conditions. Taxa from Firmicutes, Proteobacteria, and Actinobacteria were the most abundant in normal-weight and overweight/obese children, with species belonging to the genera Enterococcus, Escherichia, Staphylococcus, Bacillus, and Clostridium. Secondly, the representative isolated taxa from normal-weight vs. overweight/obese were grouped as BPA biodegrader, tolerant, or resistant bacteria, according to the presence of genes encoding BPA enzymes in their whole genome sequences. Remarkably, the presence of sporobiota and concretely Bacillus spp. showed the higher BPA biodegradation potential in overweight/obese group compared to normal-weight, which could drive a relevant role in obesity and metabolic dysbiosis triggered by these xenobiotics.

The urobiome, urinary tract infections, and the need for alternative therapeutics

Improvements in bacterial culturing and DNA sequencing techniques have revealed a diverse, and hitherto unknown, urinary tract microbiome (urobiome). The potential role of this microbial community in contributing to health and disease, particularly in the context of urinary tract infections (UTIs) is of significant clinical importance. However, while several studies have confirmed the existence of a core urobiome, the role of its constituent microbes is not yet fully understood, particularly in the context of health and disease. Herein, we review the current state of the art, concluding that the urobiome represents an important component of the body's innate immune defences, and a potentially rich resource for the development of alternative treatment and control strategies for UTIs.

The oesophageal microbiome and cancer: hope or hype?

The human oesophagus is home to a complex microbial community, the oesophageal microbiome. Despite decades of work, we still have only a poor, low-resolution view of this community, which makes it hard to distinguish hope from hype when it comes to assessing links between the oesophageal microbiome and cancer. Here we review the potential importance of this microbiome and discuss new approaches, including culturomics, metagenomics, and recovery of whole-genome sequences, that bring renewed hope for an in-depth characterisation of this community that could deliver translational impact.