Optimized DNA extraction and purification method for characterization of bacterial and fungal communities in lung tissue samples

Pneumocystis jirovecii is a potential pivotal ecological driver contributing to shifts in microbial equilibrium during the early-life lower airway microbiome assembly

Early life gut microbiota is being increasingly recognized as a major contributor to short and/or long-term human health and diseases. However, little is known about these early-life events in the human microbiome of the lower respiratory tract. This study aims to investigate fungal and bacterial colonization in the lower airways over the first year of life by analyzing lung tissue from autopsied infants. The fungal and bacterial communities of lung tissue samples from 53 autopsied infants were characterized by Next-Generation Sequencing (NGS), based on universal PCR amplification of the ITS region and the 16S rRNA gene, respectively. Our study highlights a high degree of inter-individual variability in both fungal and bacterial communities inhabiting the infant lung. The lower respiratory tract microbiota is mainly composed of transient microorganisms that likely travel from the upper respiratory tract and do not establish permanent residence. However, it could also contain some genera identified as long-term inhabitants of the lung, which could potentially play a role in lung physiology or disease. At 3-4 months of age, important dynamic changes to the microbial community were observed, which might correspond to a transitional time period in the maturation of the lung microbiome. This timeframe represents a susceptibility period for the colonization of pathogens such as Pneumocystis. The asymptomatic colonization of Pneumocystis was associated with changes in the fungal and bacterial communities. These findings suggest that the period of 2-4 months of age is a "critical window" early in life. Pneumocystis jirovecii could be a potential pivotal ecological driver contributing to shifts in microbial equilibrium during the early-life lower airway microbiome assembly, and to the future health of children.

Optimizing fungal DNA extraction and purification for Oxford Nanopore untargeted shotgun metagenomic sequencing from simulated hemoculture specimens

Long-read metagenomics provides a promising alternative approach to fungal identification, circumventing methodological biases, associated with DNA amplification, which is a prerequisite for DNA barcoding/metabarcoding based on the primary fungal DNA barcode (Internal Transcribed Spacer (ITS) region). However, DNA extraction for long-read sequencing-based fungal identification poses a significant challenge, as obtaining long and intact fungal DNA is imperative. Comparing different lysis methods showed that chemical lysis with CTAB/SDS generated DNA from pure fungal cultures with high yields (ranging from 11.20 ± 0.17 µg to 22.99 ± 2.22 µg depending on the species) while preserving integrity. Evaluating the efficacy of human DNA depletion protocols demonstrated an 88.73% reduction in human reads and a 99.53% increase in fungal reads compared to the untreated yeast-spiked human blood control. Evaluation of the developed DNA extraction protocol on simulated clinical hemocultures revealed that the obtained DNA sequences exceed 10 kb in length, enabling a highly efficient sequencing run with over 80% active pores. The quality of the DNA, as indicated by the 260/280 and 260/230 ratios obtained from NanoDrop spectrophotometer readings, exceeded 1.8 and 2.0, respectively. This demonstrated the great potential of the herein optimized protocol to extract high-quality fungal DNA from clinical specimens enabling long-read metagenomics sequencing.

IMPORTANCE

A novel streamlined DNA extraction protocol was developed to efficiently isolate high molecular weight fungal DNA from hemoculture samples, which is crucial for long-read sequencing applications. By eliminating the need for labor-intensive and shear-force-inducing steps, such as liquid nitrogen grinding or bead beating, the protocol is more user-friendly and better suited for clinical laboratory settings. The automation of cleanup and extraction steps further shortens the overall turnaround time to under 6 hours. Although not specifically designed for ultra-long DNA extraction, this protocol effectively supports fungal identification through Oxford Nanopore Technology (ONT) sequencing. It yields high molecular weight DNA, resulting in longer sequence fragments that improve the number of fungal reads over human reads. Future improvements, including adaptive sampling technology, could further simplify the process by reducing the need for human DNA depletion, paving the way for more automated, bioinformatics-driven workflows.

Exploring the impact of orthodontic appliances on the oral microbiome and inflammatory parameters

BACKGROUND

The symbiotic relationship between the oral microbiome and the host immune system is a prerequisite of oral health. Disruptions to this system can be associated with the development of diseases like dental caries. Introducing orthodontic treatments, such as aligners and fixed appliances, might impact this microbial ecosystem. This study evaluated potential changes in salivary microbiome and the level of inflammatory marker myeloid-related protein 8/14 in patients undergoing orthodontic treatment with aligners or fixed appliances.

METHODS

Forty-eight patients were divided into two groups for treatment with fixed appliances or clear aligners. Unstimulated saliva samples were collected at baseline, three, and six months for microbiome analysis via 16 S rRNA sequencing and MRP-8/14 level measurement using ELISA.

RESULTS

Among 503 identified microbial species, no significant changes were noted in overall microbiome. A considerable increase of caries-relevant species could not be observed either. MRP-8/14 levels remained unchanged across treatments, indicating no alterations in the inflammatory level.

CONCLUSION

Orthodontic treatment with fixed or removable appliances does not significantly alter the salivary microbiome or influence inflammation, suggesting that these interventions are unlikely to affect oral health negatively.

The Microbiota of the Outer Gut Mucus Layer of the Migrating Northeast Arctic Cod (Gadus morhua) as Determined by Shotgun DNA Sequencing

Animals form functional units with their microbial communities, termed metaorganisms. Despite extensive research on some model animals, microbial diversity in many species remains unexplored. Here, we describe the taxonomic profile of the microbes from the outer gut mucus layer from the Northeast Arctic cod using a shotgun DNA sequencing approach. We focused on the mucus to determine if its microbial composition differs from that of the fecal microbiota, which could reveal unique microbial interactions and functions. Metagenomes from six individuals were analyzed, revealing three different taxonomic profiles: Type I is dominated in numbers by Pseudomonadaceae (44%) and Xanthomonadaceae (13%), Type II by Vibrionaceae (65%), and Type III by Enterobacteriaceae (76%). This stands in sharp contrast to the bacterial diversity of the transient gut content (i.e., feces). Additionally, binning of assembled reads followed by phylogenomic analyses place a high-completeness bin of Type I within the Pseudomonas fluorescens group, Type II within the Photobacterium phosphoreum clade, and Type III within the Escherichia/Shigella group. In conclusion, we describe the adherent bacterial diversity in the Northeast Arctic cod's intestine using shotgun sequencing, revealing different taxonomic profiles compared to the more homogenous transient microbiota. This suggests that the intestine contains two separate and distinct microbial populations.

Optimization of lung tissue pre-treatment by bead homogenization for subsequent culturomics

The discovery that the lung harbors a diverse microbiome, as revealed by next-generation sequencing, has significantly altered our understanding of respiratory health and disease. Despite the association between the lung microbiota and disease, the nature of their relationship remains poorly understood, and culture isolation of these microorganisms could help to determine their role in lung physiology. Current procedures for processing samples from the lower respiratory tract have been shown to affect the viability of microorganisms, so it is crucial to develop new methods to improve their survival. This study aimed to improve the isolation and characterization of lung microorganisms using a bead-beating homogenization method in a mouse model. Microsphere diameter and bead-beating time affected the survival of the microorganisms (E. coli, S. aureus and C. albicans). Using 2.3 mm diameter microspheres for 60 s of bead-beating promoted the survival of both bacteria and yeast strains. After intratracheal instillation of these microorganisms in mice, approximately 70% of the cells were recovered after the tissue homogenization. To assess the efficiency of the proposed method, the diversity of bacteria was compared between the homogenate and lung tissue samples. Ninety-one genera were detected in the lung tissue, and 63 in the homogenate. Bacterial genera detected in the homogenate represented 84% of the total abundance of the microbiota identified in the lung tissue. Taken together, these results demonstrate that the tissue homogenization process developed in this study recovered the majority of the microorganisms present in the lung. This study presents a bead-beating homogenization method for effective cultivation of lung tissue microorganisms, which may help to improve the understanding of host-microbe interactions in the lung.

Gut microbiota genome features associated with brain injury in extremely premature infants

Severe brain damage is common among premature infants, and the gut microbiota has been implicated in its pathology. Although the order of colonizing bacteria is well described, the mechanisms underlying aberrant assembly of the gut microbiota remain elusive. Here, we employed long-read nanopore sequencing to assess abundances of microbial species and their functional genomic potential in stool samples from a cohort of 30 extremely premature infants. We identify several key microbial traits significantly associated with severe brain damage, such as the genomic potential for nitrate respiration and iron scavenging. Members of the Enterobacteriaceae were prevalent across the cohort and displayed a versatile metabolic potential, including pathogenic and nonpathogenic traits. Predominance of Enterobacter hormaechei and Klebsiella pneumoniae were associated with an overall loss of genomic functional redundancy as well as poor neurophysiological outcome. These findings reveal microbial traits that may be involved in exacerbating brain injury in extremely premature infants and provide suitable targets for therapeutic interventions.

Characteristics of the esophageal microbiome in patients with achalasia and its changes before and after peroral endoscopic myotomy: A pilot study

BACKGROUND AND AIM

Achalasia often presents with chronic food stasis and fermentation in the esophageal lumen, which may lead to alterations of the esophageal microbiome, with associated mucosal inflammation and dysplastic changes. The study aims to evaluate the characteristics of the esophageal microbiome in achalasia and changes of the esophageal microbiome before and after peroral endoscopic myotomy (POEM).

METHODS

This is a prospective case-control study. This study enrolled patients with achalasia and asymptomatic subjects as control group. Endoscopic brushing for esophageal microbiome collection was performed in all subjects, with additional follow-up endoscopy and brushing 3 months after POEM in achalasia patients. The composition of the esophageal microbiome was determined and compared between (1) achalasia patients and asymptomatic controls and (2) achalasia patients before and after POEM.

RESULTS

Thirty-one achalasia patients (mean age 53.5 ± 16.2 years; male 45.2%) and 15 controls were analyzed. We observed a distinct esophageal microbial community structure in achalasia patients, with increased Firmicutes and decreased Proteobacteria when compared with the control group at the phylum level. The discriminating enriched genera in achalasia patients were Lactobacillus, followed by Megasphaera and Bacteroides, and the amount of Lactobacillus was associated with the severity of achalasia. Twenty patients were re-examined after POEM, and a high prevalence of erosive esophagitis (55%) was noted, alongside an increase in genus Neisseria and decrease in Lactobacillus and Bacteroides.

CONCLUSIONS

The altered esophageal microenvironment in achalasia leads to dysbiosis with a high abundance of genus Lactobacillus. Increased Neisseria and decreased Lactobacillus were observed after POEM. The long-term effect of microbial changes warrants further study.

Advances in experimental and computational methodologies for the study of microbial-surface interactions at different omics levels

The study of the biological response of microbial cells interacting with natural and synthetic interfaces has acquired a new dimension with the development and constant progress of advanced omics technologies. New methods allow the isolation and analysis of nucleic acids, proteins and metabolites from complex samples, of interest in diverse research areas, such as materials sciences, biomedical sciences, forensic sciences, biotechnology and archeology, among others. The study of the bacterial recognition and response to surface contact or the diagnosis and evolution of ancient pathogens contained in archeological tissues require, in many cases, the availability of specialized methods and tools. The current review describes advances in in vitro and in silico approaches to tackle existing challenges (e.g., low-quality sample, low amount, presence of inhibitors, chelators, etc.) in the isolation of high-quality samples and in the analysis of microbial cells at genomic, transcriptomic, proteomic and metabolomic levels, when present in complex interfaces. From the experimental point of view, tailored manual and automatized methodologies, commercial and in-house developed protocols, are described. The computational level focuses on the discussion of novel tools and approaches designed to solve associated issues, such as sample contamination, low quality reads, low coverage, etc. Finally, approaches to obtain a systems level understanding of these complex interactions by integrating multi omics datasets are presented.

Evaluation of different DNA extraction methods based on steel-bullet beating for molecular diagnosis of onychomycosis

BACKGROUND

Considering increased trends toward molecular methods for detection/identification of fungi causing onychomycosis, the aim of this study is comparison three DNA extraction methods based on steel-bullet beating to extract DNA from nail.

METHODS

Ex -vivo onychomycosis model was developed using bovine hoof with Candida albicans and Aspergillus flavus. For two models, total DNA was extracted using the three different methods. In method 1, the extraction and purification were performed by steel-bullet beating and phenol chloroform protocol, respectively. In method 2, a freezing step were applied before beating. The purification step in method 3 was carried out using a commercial kit, although DNA extraction was done similarly to method 1 in that approach. To evaluate the efficacy of each method, the extracted genomic DNA was amplified with Polymerase Chain Reaction (PCR) using Internal Transcribed Spacer (ITS) regions. Moreover, 50 nail samples were evaluated for onychomycosis using direct microscopy examination as well as PCR in order to evaluate the diagnostic efficiency of the optimal DNA extraction method.

RESULTS

Regarding the desirable quality of the extracted DNA, cost effectiveness, and simplicity, method 1 could be used to extract DNA effectively. Additionally, the obtained data showed that PCR had a higher detection rate of fungal agents in the nail samples than direct microscopic examination.

CONCLUSIONS

This study demonstrated that the mechanical disruption of the cell wall by steel-bullet beating is a useful and practical method to improve the quantity and quality of fungal DNA thorough the extraction process.

Reducing human DNA bias in cystic fibrosis airway specimens for microbiome analysis

Next generation sequencing (NGS) has transformed our understanding of airway microbiology, however there are methodology limitations that require consideration. The presence of high concentrations of human DNA in clinical specimens can significantly impact sequencing of the microbiome, especially in low biomass samples. Here we compared three different methods (0.025% saponin, NEBNext Microbiome DNA enrichment kit, QIAamp DNA microbiome kit) for the reduction of human DNA from six CF sputum samples and determined the impact on the microbiome detected using 16S rRNA gene sequencing. Human DNA in undepleted CF sputum accounted for 94.3% of the total DNA. Saponin, the NEBNext kit and the QIAamp kit reduced human DNA levels by an average of 38.7%, 61.8% and 94.8%, respectively. None of the depletion methods reduced total bacterial DNA concentrations. QIAamp depletion did not influence taxa richness or alpha diversity however alterations to the core genera were noted following depletion. While all methods reduced human DNA in the CF sputum samples, the QIAamp DNA microbiome kit reduced Human DNA levels significantly while leaving bacterial DNA levels unchanged. Human DNA depletion in low biomass, human DNA-dense CF sputum samples is vital for improving bacterial resolution in the CF airway microbiome.

An optimized approach for processing of frozen lung and lavage samples for microbiome studies

The respiratory tract has a resident microbiome with low biomass and limited diversity. This results in difficulties with sample preparation for sequencing due to uneven bacteria-to-host DNA ratio, especially for small tissue samples such as mouse lungs. We compared effectiveness of current procedures used for DNA extraction in microbiome studies. Bronchoalveolar lavage fluid (BALF) and lung tissue samples were collected to test different forms of sample pre-treatment and extraction methods to increase bacterial DNA yield and optimize library preparation. DNA extraction using a pre-treatment method of mechanical lysis (lung tissue) and one-step centrifugation (BALF) increased DNA yield and bacterial content of samples. In contrast, a significant increase of environmental contamination was detected after phenol chloroform isoamyl alcohol (PCI) extraction and nested PCR. While PCI has been a standard procedure used in microbiome studies, our data suggests that it is not efficient for DNA extraction of frozen low biomass samples. Finally, a DNA Enrichment kit was tested and found to improve the 16S copy number of lung tissue with a minor shift in microbial composition. Overall, we present a standardized method to provide high yielding DNA and improve sequencing coverage of low microbial biomass frozen samples with minimal contamination.

Aberrant gut-microbiota-immune-brain axis development in premature neonates with brain damage

Premature infants are at substantial risk for suffering from perinatal white matter injury. Though the gut microbiota has been implicated in early-life development, a detailed understanding of the gut-microbiota-immune-brain axis in premature neonates is lacking. Here, we profiled the gut microbiota, immunological, and neurophysiological development of 60 extremely premature infants, which received standard hospital care including antibiotics and probiotics. We found that maturation of electrocortical activity is suppressed in infants with severe brain damage. This is accompanied by elevated γδ T cell levels and increased T cell secretion of vascular endothelial growth factor and reduced secretion of neuroprotectants. Notably, Klebsiella overgrowth in the gut is highly predictive for brain damage and is associated with a pro-inflammatory immunological tone. These results suggest that aberrant development of the gut-microbiota-immune-brain axis may drive or exacerbate brain injury in extremely premature neonates and represents a promising target for novel intervention strategies.