Mechanisms of microbial co-aggregation in mixed anaerobic cultures.

Co-aggregation of anaerobic microorganisms into suspended microbial biofilms (aggregates) serves ecological and biotechnological functions. Tightly packed aggregates of metabolically interdependent bacteria and archaea play key roles in cycling of carbon and nitrogen. Additionally, in biotechnological applications, such as wastewater treatment, microbial aggregates provide a complete metabolic network to convert complex organic material. Currently, experimental data explaining the mechanisms behind microbial co-aggregation in anoxic environments is scarce and scattered across the literature. To what extent does this process resemble co-aggregation in aerobic environments? Does the limited availability of terminal electron acceptors drive mutualistic microbial relationships, contrary to the commensal relationships observed in oxygen-rich environments? And do co-aggregating bacteria and archaea, which depend on each other to harvest the bare minimum Gibbs energy from energy-poor substrates, use similar cellular mechanisms as those used by pathogenic bacteria that form biofilms? Here, we provide an overview of the current understanding of why and how mixed anaerobic microbial communities co-aggregate and discuss potential future scientific advancements that could improve the study of anaerobic suspended aggregates. KEY POINTS: • Metabolic dependency promotes aggregation of anaerobic bacteria and archaea • Flagella, pili, and adhesins play a role in the formation of anaerobic aggregates • Cyclic di-GMP/AMP signaling may trigger the polysaccharides production in anaerobes.

Oral probiotic activities and biosafety of Lactobacillus gasseri HHuMIN D.

BACKGROUND: Lactobacillus spp. have been researched worldwide and are used in probiotics, but due to difficulties with laboratory cultivation of and experimentation on oral microorganisms, there are few reports of Lactobacillus spp. being isolated from the oral cavity and tested against oral pathogens. This research sought to isolate and determine the safety and inhibitory capabilities of a Lactobacillus culture taken from the human body. RESULTS: One organism was isolated, named "L. gasseri HHuMIN D", and evaluated for safety. A 5% dilution of L. gasseri HHuMIN D culture supernatant exhibited 88.8% inhibition against halitosis-producing anaerobic microorganisms and the organism itself exhibited powerful inhibitory effects on the growth of 11 oral bacteria. Hydrogen peroxide production reached 802 µmol/L after 12 h and gradually diminished until 24 h, it efficiently aggregated with P. catoniae and S. sanguinis, and it completely suppressed S. mutans-manufactured artificial dental plaque. L. gasseri HHuMIN D's KB cell adhesion capacity was 4.41 cells per cell, and the cell adhesion of F. nucleatum and S. mutans diminished strongly in protection and displacement assays. CONCLUSION: These results suggest that L. gasseri HHuMIN D is a safe, bioactive, lactobacterial food ingredient, starter culture, and/or probiotic microorganism for human oral health.

Comparison of microbial community structures between mesophilic and thermophilic anaerobic digestion of vegetable waste.

The anaerobic digestion performance correlates with the functional microbial community. Mesophilic and thermophilic digestions of vegetable waste were conducted, and dynamics of the microbial community were investigated. The mesophilic and thermophilic collapsed stages occurred at organic loading rates of 1.5 and 2.0 g VS/(L d) due to the accumulation of volatile fatty acids with final concentrations of 2276 and 6476 mg/L, respectively. A high concentration of volatile fatty acids caused the severe inhibition of methanogens, which finally led to the imbalance between acetogenesis and methanogenesis. The mesophilic digestion exhibited a higher microbial diversity and richness than the thermophilic digestion. Syntrophic acetate-oxidizing coupled with hydrogenotrophic methanogenesis was the dominant pathway in the thermophilic stable system, and acetoclastic methanogenesis in the mesophilic stable system. The dominant acidogens, syntrophus, and methanogens were unclassified_f__Anaerolineaceae (8.68%), Candidatus_Cloacamonas (19.70%), Methanosaeta (6.10%), and Methanosarcina (4.08%) in the mesophilic stable stage, and Anaerobaculum (12.59%), Syntrophaceticus (4.84%), Methanosarcina (30.58%), and Methanothermobacter (3.17%) in thermophilic stable stage. Spirochaetae and Thermotogae phyla were the characteristic microorganisms in the mesophilic and thermophilic collapsed stages, respectively. These findings provided valuable information for the deep understanding of the difference of the microbial community and methane-producing mechanism between mesophilic and thermophilic digestion of vegetable waste.

An inexpensive anaerobic chamber for the genetic manipulation of strictly anaerobic bacteria.

Strictly anaerobic bacteria are important to both human health and industrial usage. These bacteria are sensitive to oxygen, therefore, it is preferable to manipulate these microbes in an anaerobic chamber. However, commercial anaerobic chambers (CACs) are expensive, making them less accessible to scientists with a limited budget, especially to those in developing countries. The high price of commercial chambers has hindered, at least partially, the progress of research on anaerobes in developing countries. In the research presented here, we developed an inexpensive and reliable anaerobic chamber and successfully achieved routine maintenance of eleven strictly anaerobic bacterial strains. Furthermore, genetic manipulation examples have been set for both Clostridioidesdifficile 630 and Clostridiumbeijerinckii NCIMB 8052 strains to validate that the chamber could applied to advanced genetic engineering of strictly anaerobes. C. difficile and C. beijerinckii were both genetically manipulated in this chamber, showing it's utility for the genetic engineering of anaerobes. Most importantly, the anaerobic chamber was 76% - 88% less expensive than a CACs and has similar functionality with regards to the cultivation and manipulation of strictly anaerobic bacteria. The anaerobic chamber described in this study will promote the research of anaerobes in developing counties and scientists who have limited research budgets.

Inhibitory effect of LL-37 and human lactoferricin on growth and biofilm formation of anaerobes associated with oral diseases.

This study was conducted to evaluate the antimicrobial potential of the antimicrobial peptides (AMP) LL-37 and human Lactoferricin (LfcinH) on the planktonic growth and biofilm formation of oral pathogenic anaerobes related to caries and periodontitis. Multi-species bacterial suspensions of either facultative anaerobic bacteria (FAB: Streptococcus mutans, Streptococcus sanguinis, Actinomyces naeslundii) or obligate anaerobic bacteria (OAB: Veillonella parvula, Parvimonas micra, Fusobacterium nucleatum) were incubated with different concentrations of AMP solutions for 8 h. Planktonic growth was registered with an ATP-based cell viability assay for FAB and via plate counting for OAB. Biofilms were grown on ZrO2 discs for 4 days in a mixture of the multi-species bacterial suspensions and AMP solutions. Biofilm mass was quantified using a microtiter plate biofilm assay with crystal violet staining. An overall planktonic growth inhibition and biofilm mass reduction of FAB and OAB was registered for LL-37 and LfcinH. Significant inhibitory threshold concentrations of LL-37 were observed in all experiments (p < 0.0001). No significant threshold was observed for LfcinH. Biofilm mass of OAB was barely reduced by LfcinH. The complete mechanisms of the AMPs are not fully understood yet. While LL-37 shows promising features as potential therapeutic for biofilm-associated oral diseases, LfcinH seems unsuitable for this particular indication. For clinical AMP use, further investigations will be necessary.

Impact of Simulated Martian Conditions on (Facultatively) Anaerobic Bacterial Strains from Different Mars Analogue Sites.

Five bacterial (facultatively) anaerobic strains, namely Buttiauxella sp. MASE-IM-9, Clostridium sp. MASE-IM-4, Halanaerobium sp. MASE-BB-1, Trichococcus sp. MASE-IM-5, and Yersinia intermedia MASE-LG-1 isolated from different extreme natural environments were subjected to Mars relevant environmental stress factors in the laboratory under controlled conditions. These stress factors encompassed low water activity, oxidizing compounds, and ionizing radiation. Stress tests were performed under permanently anoxic conditions. The survival rate after addition of sodium perchlorate (Na-perchlorate) was found to be species-specific. The inter-comparison of the five microorganisms revealed that Clostridium sp. MASE-IM-4 was the most sensitive strain (D10-value (15 min, NaClO4) = 0.6 M). The most tolerant microorganism was Trichococcus sp. MASE-IM-5 with a calculated D10-value (15 min, NaClO4) of 1.9 M. Cultivation in the presence of Na-perchlorate in Martian relevant concentrations up to 1 wt% led to the observation of chains of cells in all strains. Exposure to Na-perchlorate led to a lowering of the survival rate after desiccation. Consecutive exposure to desiccating conditions and ionizing radiation led to additive effects. Moreover, in a desiccated state, an enhanced radiation tolerance could be observed for the strains Clostridium sp. MASE-IM-4 and Trichococcus sp. MASE-IM-5. These data show that anaerobic microorganisms from Mars analogue environments can resist a variety of Martian-simulated stresses either individually or in combination. However, responses were species-specific and some Mars-simulated extremes killed certain organisms. Thus, although Martian stresses would be expected to act differentially on microorganisms, none of the expected extremes tested here and found on Mars prevent the growth of anaerobic microorganisms.

Comparative analysis of the effects of five soil fumigants on the abundance of denitrifying microbes and changes in bacterial community composition.

Soil fumigation is currently the most effective method for controlling soil-borne pests and diseases in high-value crops. To better understand the effect of chloropicrin (CP), dazomet (DZ), dimethyl disulfide (DMDS), allyl isothiocyanate (AITC) and 1,3-dichloropropene (1,3-D) fumigants on soil microorganisms, this study monitored changes in the diversity and community composition of soil bacteria involved in denitrification using real-time PCR and high-throughput gene sequencing techniques. These five fumigants significantly decreased the bacterial population size in some phyla including Proteobacteria, Chloroflexi and Acidobacteria, and increased the bacterial population size in other phyla such as Firmicutes, Gemmatimonadetes, Actinobacteria, Verrucomicrobia, Saccharibacteria and Parcubacteria. Although bacterial diversity declined after CP fumigation, it was briefly stimulated by the other four fumigants. Meanwhile, all five fumigants temporarily decreased populations of denitrifying bacteria containing the napA, narG, nirS or nirK enzyme-encoding genes. Denitrifiers bearing the cnorB, qnorB or nosZ genes were relatively stable following DZ and DMDS fumigation. However, cnorB and nosZ decreased initially following CP, AITC and 1,3-D fumigation. Simultaneously, the abundance of qnorB significantly increased in AITC and 1,3-D fumigated soils. These results showed that soil fumigation significantly shifted the abundance and community structure of denitrifying bacteria. This study will help to predict the response of different phyla of denitrifying bacteria to soil fumigation.

Characterization of medical relevant anaerobic microorganisms by isothermal microcalorimetry.

Detection of anaerobe bacteria by culture methods requires appropriate media, special growth conditions, additional detection techniques and it typically takes several days. Therefore, anaerobes are often missed in patient specimens under routine culture conditions. Microcalorimetry may provide a simple and accurate real-time method for faster and better detection of anaerobes. An isothermal calorimeter which detect minimal changes of temperature over time was used for the calorimetric experiments. In order to find optimal growth conditions, seven reference or clinical strains of medical relevant anaerobe bacteria were tested under different circumstances. First, the strains were tested with different growth media. After determining the optimal medium for each strain, the gas phase was modified by adding 3 mL or 4 mL medium, to evaluate growth under conditions with less oxygen. Cooked Meat Medium was best supporting growth of the tested strains, including Cutibacterium acnes, Fusobacterium nucleatum, Finegoldia magna, Parvimonas micra, Bacteroides fragilis and Actinomyces odontolyticus, followed by thioglycolate. The best medium to detect Clostridioides difficile was H-Medium. All tested strains showed better growth in 4 mL medium than in 3 mL. The detection time ranged between 10 and 72 h. Our results demonstrated that the sensitivity and the detection time of anaerobe bacteria can be improved by isothermal calorimetry with optimization of growth conditions. Therefore, calorimetric detection, a practical, quick and easy-to-do method, has the potential to replace current microbiological methods.

Improvement of a disk diffusion method for antibiotic susceptibility testing of anaerobic bacteria. French recommendations revisited for 2020.

The disk diffusion test is very popular but for anaerobes the main pitfalls arise from the significant variation of diameters for an individual MIC and the weak correlation observed between the MIC's values and diameters zone that generates many major and very major errors. AIMS OF THE STUDY: without any change in the methodology and revisiting only new diameter breakpoints, we try to improve the previous French recommendations and therefore decrease number of errors by introducing recent EUCAST concepts such as ECOFF and ATU Zone. METHOD: MIC determination by agar dilution was done on 100 anaerobes against 6 antibiotics. Clinical categorization was based on EUCAST Breakpoints. Disk-diffusion method was realized on the same Brucella blood agar incubated in an anaerobic chamber. 550 categorizations by both methods could be done as amoxicillin was not tested on the 50 B. fragilis group. As anaerobic infections are severe and treated by antibiotics at higher dosage, we focus on resistance breakpoint to avoid mainly very major errors (VME). Distribution of inhibition zones for each MIC allow us to fix the zone diameter breakpoints. These results were matched to a large data on distribution of zone diameters for each antibiotic collected from two French hospitals from 1990 to 2005. As example for metronidazole and the B. fragilis group, we calculated the cut-off diameter (15 mm) from a wild type population, at a time when there was no resistance to this antibiotic and observed that it was identical to the diameter breakpoint for susceptibility. RESULTS: For an individual value of MIC, the distribution of diameters is wider for anaerobes especially for clindamycin and metronidazole. Using a 15 mm breakpoint for these two antibiotics limits dramatically the number of very major errors but slowly increases the number of major errors that could be overcome by MIC determination if inhibition zone is less than 15 mm. ATU zones (Area of technical uncertainty) were introduced for amoxicillin-clavulanate (17-20 mm), piperacillin-tazobactam (17-20 mm), imipenem (18-23 mm). Categorization inside the ATU requires MIC determination. Finally, out of 550 determinations, VME were observed in 1.45% of cases, an acceptable rate. CONCLUSION: in combination with introduction of ATU zones disk diffusion method allows to detect resistant strains with little MIC determinations and very major errors.

Clinical utility of anaerobic culture of cerebrospinal fluid.

Anaerobic meningitis is a rare serious clinical condition which mainly affects vulnerable populations and patients with predisposing factors such as head trauma, prior neurosurgical procedures or implantable medical devices such as ventriculoperitoneal shunts or ventricular drains. In this study we retrieved data from aerobic and anaerobic cultures of cerebrospinal (CSF) or ventricular fluid ordered over a 5 year period at our institution. A total of 8868 aerobic and 594 anaerobic cultures were performed from 2013 to 2017. 24/594 (4%) anaerobic cultures from 14 patients were positive for anaerobes. Only 3 of those patients were diagnosed clinically with anaerobic meningitis, each with predisposing factors, while anaerobes (Cutibacterium acnes and Clostridium perfringens) recovered from the remaining 21 patients were regarded as contaminants. 129/8868 (1.45%) aerobic CSF cultures were positive for anaerobes. 120/129 (93%) cultures recovered C. acnes while non-C. acnes anaerobes were recovered in the remaining 9 cultures and were deemed to be contaminants. In the majority of situations, recovery of C. acnes from CSF or ventricular fluid was regarded as contamination. Our cohort included 18 patients with a ventriculoperitoneal shunt or ventricular drain, 17 of whom had C. acnes recovered from either aerobic or anaerobic culture, and 10 were treated with targeted antibiotics and surgical replacement of the shunt or drain. Anaerobic culture of the CSF or ventricular fluid aided in identification of two patients with anaerobic meningitis and an additional two patients with shunt infection. Anaerobe culture of CSF is important in identification of anaerobic meningitis, as growth of anaerobes other than C. acnes is rare from aerobic CSF culture.

Microbial community dynamics during anaerobic co-digestion of corn stover and swine manure at different solid content, carbon to nitrogen ratio and effluent volumetric percentages.

The methane production and the microbial community dynamics of thermophilic anaerobic co-digestion (AD) of corn stover, swine manure and effluent were conducted at total solid (TS) content of 5%, 10% and 15%, the carbon to nitrogen ratio (C/N) of 20, 30 and 40 and the effluent volumetric percentage (EVP) of 20%, 40% and 60%. For batches with 5% TS, the highest methane yield of 238.5-283.1 mL g-1 volatile solid (VS) and the specific methane productivity of 138.5-152.2 mL g-1 initial VS were obtained at the C/N ratios of 20 and 30. For the mixtures with 10% and 15% TS, the highest methane yield was 341.9 mL g-1 VS and 351.2 mL g-1 VS, respectively, when the C/N ratio of 20% and 60% EVP conditions were maintained. Co-digestion of swine manure with corn stover caused an obvious shift in microbial population, in which the archaeal population changed from 0.3% to 2.8% and the bacterial community changed from 97.2% to 99.7%. The experimental batches with the highest relative abundance of the archaeal population (2.00% of total microbial population for 5% TS, 1.74% for 10% TS and 2.76% for 15% TS) had the highest rate of methanogenesis subsequently enhancing methane production (283.08 mL g-1 VS for 5% TS, 341.91 mL g-1 VS for 10% TS and 351.23 mL g-1 VS for 15% TS). The results of microbiome analysis enabled understanding the key populations in biomethane generation.

Biotreatment of high-salinity wastewater: current methods and future directions.

Saline wastewaters are usually generated by various industries, including the chemical, pharmaceutical, agricultural, and aquacultural industries. The discharge of untreated high-salinity wastewater may cause serious environmental pollution and damage the aquatic, terrestrial, and wetland ecosystems. For many countries, the treatment of saline wastewater has become an important task. Generally, saline wastewaters are treated through physical and chemical methods. However, these traditional techniques are associated with higher treatment costs and the generation of byproducts. In contrast, biotreatment techniques are environmentally friendly and inexpensive. This review highlights the sources and environmental concerns of high-salinity wastewater and illustrates the latest problems and solutions to the use of biological approaches for treating saline wastewater. Although high salinity may inhibit the effectiveness of aerobic and anaerobic biological wastewater treatment methods, such strategies as selecting salt-adapted microorganisms capable of degrading pollutants with tolerance to high salinity and optimizing operating conditions can be effective. This mini-review may serve as a reference for future efforts to treat high-salinity wastewater.

Anaerobes in cystic fibrosis patients' airways.

Anaerobes are known to constitute an important part of the airway microbiota in both healthy subjects and cystic fibrosis (CF) patients. Studies on the potential role of anaerobic bacteria in CF and thus their involvement in CF pathophysiology have reported contradictory results, and the question is still not elucidated. The aim of this study was to summarize anaerobe diversity in the airway microbiota and its potential role in CF, to provide an overview of the state of knowledge on anaerobe antibiotic resistances (resistome), and to investigate the detectable metabolites produced by anaerobes in CF airways (metabolome). This review emphasizes key metabolites produced by strict anaerobic bacteria (sphingolipids, fermentation-induced metabolites and metabolites involved in quorum-sensing), which may be essential for the better understanding of lung disease pathophysiology in CF.

Interactions between anaerobic ammonium- and methane-oxidizing microorganisms in a laboratory-scale sequencing batch reactor.

The reject water of anaerobic digestors still contains high levels of methane and ammonium that need to be treated before these effluents can be discharged to surface waters. Simultaneous anaerobic methane and ammonium oxidation performed by nitrate/nitrite-dependent anaerobic methane-oxidizing(N-damo) microorganisms and anaerobic ammonium-oxidizing(anammox) bacteria is considered a potential solution to this challenge. Here, a stable coculture of N-damo archaea, N-damo bacteria, and anammox bacteria was obtained in a sequencing batch reactor fed with methane, ammonium, and nitrite. Nitrite and ammonium removal rates of up to 455 mg N-NO2- L-1 day-1 and 228 mg N-NH4+ L-1 were reached. All nitrate produced by anammox bacteria (57 mg N-NO3- L-1 day-1) was consumed, leading to a nitrogen removal efficiency of 97.5%. In the nitrite and ammonium limited state, N-damo and anammox bacteria each constituted about 30-40% of the culture and were separated as granules and flocs in later stages of the reactor operation. The N-damo archaea increased up to 20% and mainly resided in the granular biomass with their N-damo bacterial counterparts. About 70% of the nitrite in the reactor was removed via the anammox process, and batch assays confirmed that anammox activity in the reactor was close to its maximal potential activity. In contrast, activity of N-damo bacteria was much higher in batch, indicating that these bacteria were performing suboptimally in the sequencing batch reactor, and would probably be outcompeted by anammox bacteria if ammonium was supplied in excess. Together these results indicate that the combination of N-damo and anammox can be implemented for the removal of methane at the expense of nitrite and nitrate in future wastewater treatment systems.

Salinity-driven heterogeneity toward anammox distribution and growth kinetics.

Anaerobic ammonium oxidation (anammox) has been widely applied for biological nitrogen removal in freshwater systems, and there is a potential for its extension in saline water systems. In this study, the abundance and biodiversity of anammox bacteria were investigated in both saline and freshwater full-scale sewage treatment plants (STPs). The anammox bacteria were widely found in four tested STPs with abundance of 105-107 copies per mL of 16S rRNA gene. Phylogenetic results showed that Ca. Scalindua and Ca. Brocadia dominated in saline and freshwater STPs, respectively. Ca. Kuenenia dominated in one of freshwater STPs. However, redundancy discriminate analysis (RDA) indicates the distribution of Ca. Kuenenia in both saline and freshwater conditions. To further elucidate these observations, the Monod model was integrated with Gauss equation for the evaluation of salinity-induced kinetics. Model results reveal that when nitrite concentration (SNO2-) is higher than nitrite affinity constant (KNO2-), salinity (over ~ 3.0%) is responsible for Candidatus Scalindua dominance over Candidatus Kuenenia. Conversely, in nitrite-depleted conditions (KNO2- ≥ SNO2-), high nitrite affinity leads to the predominance of Ca. Scalindua in all salinities. This study provides fundamental insights into saline anammox applications.

Short-term culture for rapid identification of anaerobic bacteria from blood cultures.

Identification of anaerobic bacteria causing blood stream infections (BSI) is challenging. This study describes the epidemiology of anaerobic BSI at a tertiary care hospital and the performance of a rapid method for identification of anaerobic bacteria from blood cultures over three years, between June 2015 and June 2018. Short-term culturing is a low-cost user-friendly method and may be used for rapid identification of bacteria from positive blood cultures by matrix-associated laser desorption ionization time of flight (MALDI-TOF). Short-term culturing is performed after Gram staining on all positive blood culture bottles (BCBs) before 10:30 a.m. in our laboratory. Successful short-term cultures were defined as growth and reliable MALDI-TOF result in maximum 8 h after culture positivity. Data pertaining to unique anaerobic episodes and short-term cultures was collected retrospectively from our laboratory information system. Overall, during the three-year period, 692 unique anaerobic episodes (including Propionibacterium spp) were isolated. A total of 17 anaerobic bacterial genera were isolated in our laboratory, with 5 GNB genera and 12 GPB genera. The most prevalent bacteria were Bacteroides spp. 266/692 (38%), Propionibacterium spp. 128/692 (18%), Clostridium spp. 103/692 (15%), Fusobacterium spp. 34/692 (5%), and Actinomyces spp. 34/692 (5%). We performed short-term cultures on 270/564 (48%) clinically relevant episodes (excluding Propionibacterium spp) on chocolate agar plates. Growth within 8 h from culture positivity was detected in 33/270 (12%) short-term cultures. There were 22/33 (67%) gram negative (GNB) and 11/33 (33%) gram positive bacteria (GPB). Only two genera were identified: Bacteroides spp 22/33 (67%) and Clostridium spp 11/33 (33%). Thus, short-term culturing can function as a low-cost add-on to already existing protocols involving MALDI-TOF, where both GNB and GPB can be identified.

Aerobic and anaerobic enrichment cultures highlight the pivotal role of facultative anaerobes in soil hydrocarbon degradation.

Aliphatic and aromatic hydrocarbons are ubiquitous in the environment due to natural and anthropogenic processes. Under aerobic conditions hydrocarbons can be rapidly biodegraded but oxygenated environments often quickly become anaerobic when microbial respiration is coupled to contaminant oxidation. Most studies in literature usually focus on the initial microbial diversity of the hydrocarbon impacted environment and examine either aerobic or anaerobic conditions for enrichment. Hence, the aim of the present study was to enrich bacterial consortiums from two diesel impacted soil samples under both these conditions to assess the enrichment diversities and hydrocarbon degradation potentials. This would shed light upon how an environmental population shift would correlate to oxygen intrusion and depletion and still continue hydrocarbon degradation. Analysis of the 16S rRNA gene sequences showcases the different microbial populations that could emerge as the environmental factors change, resulting in different populations that are still capable of hydrocarbon degradation. Microbial diversity analysis also highlights the role of facultative anaerobic bacteria like Pseudomonas spp. and Citrobacter spp. in maintaining hydrocarbon degradation. This study shows that microorganisms capable of surviving under both oxic and anoxic (aerobic and anaerobic) conditions are the most crucial to the long term degradation of hydrocarbons in the environment.

Enhancing hydrogen production through anaerobic co-digestion of fruit waste with biosolids.

In the present study, anaerobic co-digestion process was carried out with 23 mixed substrates proportion (MSP) of fruit waste (FRW), municipal wastewater treatment plant aerated biosolid (MPABS) and dairy effluent treatment plant returned biosolid (DPRBS). During co-digestion process, the effect of MSP on carbon/nitrogen (C/N) ratio and hydrogen production was investigated. The results revealed that MSP17 (70 FRW:20 MPABS:10 DPRBS) has yielded maximal hydrogen production of 295 mL with C/N ratio of 30, followed by MSP9 (70 FRW:30 DPRBS) exhibiting 253 mL of hydrogen production with C/N ratio of 29 and MSP2 (90 FRW:10 MPABS) attained 223 mL of hydrogen production with C/N ratio of 27. Then, SEM analysis of digested substrate sample was also performed in which flocs observed to be small and loose in structure in co-digested samples and intact form in non co-digested samples. Hence, this study results can be used for a sustainable approach by utilizing the FRW and biosolids for hydrogen production.

Dynamics of Archaeal and Bacterial Communities in Response to Variations of Hydraulic Retention Time in an Integrated Anaerobic Fluidized-Bed Membrane Bioreactor Treating Benzothiazole Wastewater.

An integrated anaerobic fluidized-bed membrane bioreactor (IAFMBR) was investigated to treat synthetic high-strength benzothiazole wastewater (50 mg/L) at a hydraulic retention time (HRT) of 24, 18, and 12 h. The chemical oxygen demand (COD) removal efficiency (from 93.6% to 90.9%), the methane percentage (from 70.9% to 69.27%), and the methane yield (from 0.309 m3 CH4/kg·CODremoved to 0.316 m3 CH4/kg·CODremoved) were not affected by decreasing HRTs. However, it had an adverse effect on membrane fouling (decreasing service period from 5.3 d to 3.2 d) and benzothiazole removal efficiency (reducing it from 97.5% to 82.3%). Three sludge samples that were collected on day 185, day 240, and day 297 were analyzed using an Illumina® MiSeq platform. It is striking that the dominant genus of archaea was always Methanosaeta despite of HRTs. The proportions of Methanosaeta were 80.6% (HRT 24), 91.9% (HRT 18), and 91.2% (HRT 12). The dominant bacterial genera were Clostridium in proportions of 23.9% (HRT 24), 16.4% (HRT 18), and 15.3% (HRT 12), respectively.

Sample preparation method influences direct identification of anaerobic bacteria from positive blood culture bottles using MALDI-TOF MS.

Rapid detection and identification of anaerobic bacteria from blood is important to adjust antimicrobial therapy by including antibiotics with activity against anaerobic bacteria. Limited data is available about direct identification of anaerobes from positive blood culture bottles using MALDI-TOF mass spectrometry (MS). In this study, we evaluated the performance of two sample preparation protocols for direct identification of anaerobes from positive blood culture bottles, the MALDI Sepsityper kit (Sepsityper) and the in-house saponin (saponin) method. Additionally, we compared two blood culture bottle types designed to support the growth of anaerobic bacteria, the BacT/ALERT-FN Plus (FN Plus) and the BACTEC-Lytic (Lytic), and their influence on direct identification. A selection of 30 anaerobe strains belonging to 22 different anaerobic species (11 reference strains and 19 clinical isolates) were inoculated to 2 blood culture bottle types in duplicate. In total, 120 bottles were inoculated and 99.2% (n = 119) signalled growth within 5 days of incubation. The Sepsityper method correctly identified 56.3% (n = 67) of anaerobes, while the saponin method correctly identified 84.9% (n = 101) of anaerobes with at least log(score) ≥1.6 (low confidence correct identification), (p < 0.001). Gram negative anaerobes were better identified with the saponin method (100% vs. 46.5%; p < 0.001), while Gram positive anaerobes were better identified with the Sepsityper method (70.8% vs. 62.5%; p = 0.454). Average log(score) values among only those isolates that were correctly identified simultaneously by both sample preparation methods were 2.119 and 2.029 in favour of the Sepsityper method, (p = 0.019). The inoculated bottle type didn't influence the performance of the two sample preparation methods. We confirmed that direct identification from positive blood culture bottles with MALDI-TOF MS is reliable for anaerobic bacteria. However, the results are influenced by the sample preparation method used.