Selective syngas fermentation to acetate under acidic and psychrophilic conditions using mixed anaerobic culture

Syngas fermentation to acetate offers a promising solution for its valorisation, particularly when syngas contains a high N2 concentration, which otherwise impedes the utilisation of syngas biomethanation gaseous product in cogeneration or upgrading units. In this study, continuous lab-scale syngas fermentation assessing the effects of acidic pH and psychrophilic conditions (28 °C and 20 °C) on bioconversion efficiency and anaerobic consortium diversity was studied. The results showed that as temperature and pH decrease, acetate yield increases. The highest H2 and CO consumption rates were observed at 20 °C and pH 4.5, reaching 48.4 mmol/(L·d) and 31.5 mmol/(L·d), respectively, and methanogenic activity was not completely suppressed. The microbial community composition indicated an enhanced abundance of acetate-producing bacteria and hydrogenotrophic methanogens at 28 °C. The PICRUSt2 prediction of metabolic potential indicated that temperature and pH changes appear to have a more pronounced impact on acetotrophic methanogenesis genes than carbon dioxide-based methanogenesis genes.

Degradation characteristics of polyethylene film by microorganisms from lake sediments

Polyethylene (PE) exists widely in many habitats as a persistent organic pollution and poses a major threat to the ecological environment. In this study, bacterial communities in freshwater lake sediments were exposed to culture media using PE films as the sole carbon source in aerobic and anaerobic microculture environments, and they were able to adhere and adapt to the PE films for a longer period of time. The results demonstrated that the pH value of the medium in the two cultural conditions was distinct, as were the rates of films weight loss and surface functional group alterations. We also concluded the certain bacterial genera from freshwater lake sediments who may be able to degrade PE films under either aerobic or anaerobic conditions. Simultaneously, the dominating bacterial communities between the medium and the film differed significantly under two cultural settings, as did the community composition, while metabolism was the primary function.

Molecular typing of Clostridioides difficile from frozen stool samples to investigate cross-transmissions: A proof of concept

PURPOSE

Toxigenic Clostridioides difficile is responsible for up to one third of post antibiotic diarrhea and for more than 95% of pseudomembranous colitis. Nowadays, diagnosis relies on the documentation of the presence of the toxin in stools by specific antigenic or PCR tests. Stool cultures have been mostly abandoned, leading to the absence of isolates for further epidemiological analyses.

METHODS

Aliquots of stool samples, frozen for up to two years, were thawed and inoculated onto commercial C. difficile media. Eighteen stools were recovered from patients hospitalized in the pediatric ward where at that time a chain of transmission was suspected. Eleven stools were recovered from patients hospitalized in a medical ward over a three months period with no suspected transmission event. Up to 16 characteristic colonies were isolates per culture. PCR of toxins genes and molecular typing by Double Locus Sequence Typing (DLST) were performed on these colonies. Whole genome multi locus sequence typing (wgMLST) was performed on selected isolates.

RESULTS

Among the 29 stool specimens, no growth was observed for four stools and only one colony grew for one stool. Except the latter, all 16 colonies of the 24 stools showed identical toxin genes profiles than the original stool. However, variant DLST genotypes was observed within 20% of investigated stools. The majority of variants were single locus variant due to an IN/DEL of the repeat in one of the two DLST locus. Despite this variation, results of molecular typing overrule the putative transmission chain in the pediatric ward and revealed undetected chains of transmission in the medical ward. These results were confirmed with wgMLST.

CONCLUSIONS

The developed protocol allows prospective and retrospective molecular and genomic epidemiological investigation of C. difficile infections for infection control purpose.

Cultivation of gut microorganisms of the marine ascidian Halocynthia roretzi reveals their potential roles in the environmental adaptation of their host

It has long been known that abundant symbiotic bacteria exist in the tunic and gut of marine ascidians, and that these play crucial roles in host development, physiological metabolism, and environmental adaptation. However, the identity, roles and functions of these symbiotic bacteria are known for only a few strains. In this study, we isolated and cultivated 263 strains of microorganisms from the intestine of the marine ascidian Halocynthia roretzi through a combination of aerobic and anaerobic culture approaches. Most cultivated species, both aerobic and anaerobic, from ascidian stool samples belonged to the genus Bacillus based on 16S rDNA sequencing identification and phylogenetic assays. The distribution of cultured bacteria varied with seasonal changes in environmental conditions. To explore the functions of cultured bacteria, we screened out a strain of Serratia sp. whose extracts showed high antibacterial activity against aquatic pathogens. These findings revealed the potential roles of gut microorganisms in ascidian defense and environmental adaptation, thus providing insights into the interaction and co-evolution between gut bacteria and their hosts.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-022-00131-4.

Case of infant invasive Streptococcus intermedius infection suggesting the need for anaerobic cultures

We report the case of an immunocompetent 6-month-old boy with a lung abscess and empyema caused by Streptococcus intermedius detected only from anaerobic cultures. Invasive S. intermedius infection in infants is rare. S. intermedius has been infrequently reported as a causative microorganism of lung abscess and empyema as most of the S. intermedius infections in children have been head and neck infections. While anaerobic cultures are often not performed for infant patients, we suggest the need for these cultures, including blood cultures, especially in cases of pediatric empyema, brain abscess, and liver abscess, which can be caused by S. intermedius.

Enzyme functionalized microgels enable precise regulation of dissolved oxygen and anaerobe culture

Anaerobes are a major constituent of the gut microbiome and profoundly influence the overall health of humans. However, the lack of a simple, cost-effective, and scalable system that mimics the anaerobic conditions of the human gut is hindering research on the gut microbiome and the development of therapeutics. Here, we address this gap by using glucose oxidase and catalase containing gelatin microparticles (GOx-CAT-GMPs) to precisely regulate dissolved oxygen concentration [O2] via GOx-mediated consumption of oxygen. Fluorescence images generated using conjugated polymer afterglow nanoparticles showed that [O2] can be tuned from 257.9 ​± ​6.2 to 0.0 ​± ​4.0 ​μM using GOx-CAT-GMPs. Moreover, when the obligate anaerobe Bacteroides thetaiotaomicron was inoculated in media containing GOx-CAT-GMPs, bacterial growth under ambient oxygen was comparable to control conditions in an anaerobic chamber (5.4 ​× ​105 and 8.8 ​× ​105 colony forming units mL-1, respectively). Finally, incorporating GOx-CAT-GMPs into a bioreactor that permitted continuous radial diffusion of oxygen and glucose generated a gut-mimetic [O2] gradient of 132.4 ​± ​2.6 ​μM in the outer ring of the reactor to 7.9 ​± ​1.7 ​μM at the core. Collectively, these results indicate that GOx-CAT-GMPs are highly effective oxygen-regulating materials. These materials can potentially be leveraged to advance gut microbiome research and fecal microbiota transplantation, particularly in low-resource settings.

Olsenella timonensis sp. nov., a new bacteria species isolated from the human gut microbiota

Olsenella timonensis sp. nov., strain Marseille-P2300^T (= CSUR P2300; =DSM102072), is a new bacterial species from the phylum Firmicutes in the family Atopobiaceae.This bacteria species was isolated from the human gut microbiota.

Case report of Actinomyces turicensis meningitis as a complication of purulent mastoiditis

BACKGROUND

Central nervous system (CNS) infections caused by Actinomyces spp. including brain abscess, actinomycoma, subdural empyema and epidural abscess are well described, however reports of Actinomyces-associated meningitis are scarcely reported.

CASE REPORT

We present the case of a 43-year-old Hungarian male patient with poor socioeconomic status who developed acute bacterial meningitis caused by Actinomyces turicensis originating from the left side mastoiditis. The bacterial cultures of both cerebrospinal fluid (CSF) and purulent discharge collected during the mastoid surgery showed slow growing Gram-positive rods that were identified by automated systems (API, VITEK) as A. turicensis The bacterial identification was confirmed by 16S rRNA PCR and subsequent nucleic acid sequencing. No bacterial growth was detected in blood culture bottles after 5 days of incubation. Hence, multiple antibacterial treatments and surgical intervention the patient passed away.

CONCLUSIONS

Anaerobes are rarely involved in CNS infections therefore anaerobic culture of CSF samples is routinely not performed. However, anaerobic bacteria should be considered as potential pathogens when certain risk factors are present, such as paranasal sinusitis, mastoiditis in patients with poor socioeconomic condition. To the best of our knowledge, our case report is the first description of A. turicensis meningitis that has been diagnosed as consequence of purulent mastoiditis.

Anaerobic culture to detect periodontal and caries pathogens

BACKGROUND

Anaerobic culture has been critical in our understanding of the oral microbiotas.

HIGHLIGHT

Studies in advanced periodontitis in the 1970's revealed microbial complexes that associated with different clinical presentations. Taxonomy studies identified species newly-observed in periodontitis as Aggregatibacter (Actinobacillus) actinomycetemcomitans, Campylobacter (Wolinella) rectus and other Campylobacter species, and Tannerella (Bacteroides) forsythia. Anaerobic culture of initial periodontitis showed overlap in the microbiota with gingivitis, and added Selenomonas noxia and Filifactor alocis as putative periodontal pathogens. Porphyromonas gingivalis and T. forsythia were found to be associated with initial periodontitis in adults. The dominant microbiota of dental caries differs from that of periodontitis. The major cariogenic species are acidogenic and acid tolerant species particularly Streptococcus mutans, and Lactobacillus and Bifidobacterium species. Anaerobic culture of severe early childhood caries revealed a widely diverse microbiota, comparable to that observed using cloning and sequencing. The PCR-based cloning approach, however, underestimated Actinobacteria compared with culture. Only a subset of the caries-associated microbiota was acid tolerant, with different segments of the microbiota cultured on blood agar compared to a low pH acid agar. While the major caries-associated species was S. mutans, a new species, Scardovia wiggsiae, was significantly associated with early childhood caries. Higher counts of S. wiggsiae were also observed in initial white spot carious lesions in adolescents.

CONCLUSION

In periodontitis and dental caries, anaerobic culture studies of advanced disease provided a comprehensive analysis of the microbiota of these infections. Anaerobic culture highlighted the limitation of PCR with standard primers that underestimate detection of Actinobacteria.