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Foods (Basel, Switzerland) Feb 2024The primary goal of this scoping review is to collect, analyze, and critically describe information regarding the role of the main compounds (reuterin, phenyllactic... (Review)
Review
The primary goal of this scoping review is to collect, analyze, and critically describe information regarding the role of the main compounds (reuterin, phenyllactic acid, and exopolysaccharides) produced by LAB that possess antifungal properties and provide some suggestions for further research. The use of lactic acid bacteria (LAB) to mitigate spoilage and extend the shelf life of foodstuffs has a long history. Recently, there has been a growing interest in the unique properties of these additions to the foodstuffs in which they are applied. In recent studies regarding biopreservation, significant attention has been given to the role of these microorganisms and their metabolites. This fascinating recent discipline aims not only to replace traditional preservation systems, but also to improve the overall quality of the final product. The biologically active by-products produced by lactic acid bacteria are synthesized under certain conditions (time, temperature, aerobiosis, acidity, water activity, etc.), which can be enacted through one of the oldest approaches to food processing: fermentation (commonly used in the dairy and bakery sectors). This study also delves into the biosynthetic pathways through which they are synthesized, with a particular emphasis on what is known about the mechanisms of action against molds in relation to the type of food.
PubMed: 38472865
DOI: 10.3390/foods13050752 -
Microbial Physiology 2024C4-dicarboxylates (C4-DC) have emerged as significant growth substrates and signaling molecules for various Enterobacteriaceae during their colonization of mammalian...
INTRODUCTION
C4-dicarboxylates (C4-DC) have emerged as significant growth substrates and signaling molecules for various Enterobacteriaceae during their colonization of mammalian hosts. Particularly noteworthy is the essential role of fumarate respiration during colonization of pathogenic bacteria. To investigate the regulation of aerobic C4-DC metabolism, the study explored the transcriptional control of the main aerobic C4-DC transporter, dctA, under different carbohydrate conditions. In addition, mutants related to carbon catabolite repression (CCR) and C4-DC regulation (DcuS-DcuR) were examined to better understand the regulatory integration of aerobic C4-DC metabolism into CCR. For initial insight into posttranslational regulation, the interaction between the aerobic C4-DC transporter DctA and EIIAGlc from the glucose-specific phosphotransferase system was investigated.
METHODS
The expression of dctA was characterized in the presence of various carbohydrates and regulatory mutants affecting CCR. This was accomplished by fusing the dctA promoter (PdctA) to the lacZ reporter gene. Additionally, the interaction between DctA and EIIAGlc of the glucose-specific phosphotransferase system was examined in vivo using a bacterial two-hybrid system.
RESULTS
The dctA promoter region contains a class I cAMP-CRP-binding site at position -81.5 and a DcuR-binding site at position -105.5. DcuR, the response regulator of the C4-DC-activated DcuS-DcuR two-component system, and cAMP-CRP stimulate dctA expression. The expression of dctA is subject to the influence of various carbohydrates via cAMP-CRP, which differently modulate cAMP levels. Here we show that EIIAGlc of the glucose-specific phosphotransferase system strongly interacts with DctA, potentially resulting in the exclusion of C4-DCs when preferred carbon substrates, such as sugars, are present. In contrast to the classical inducer exclusion known for lactose permease LacY, inhibition of C4-DC uptake into the cytoplasm affects only its role as a substrate, but not as an inducer since DcuS detects C4-DCs in the periplasmic space ("substrate exclusion"). The work shows an interplay between cAMP-CRP and the DcuS-DcuR regulatory system for the regulation of dctA at both transcriptional and posttranslational levels.
CONCLUSION
The study highlights a hierarchical interplay between global (cAMP-CRP) and specific (DcuS-DcuR) regulation of dctA at the transcriptional and posttranslational levels. The integration of global and specific transcriptional regulation of dctA, along with the influence of EIIAGlc on DctA, fine-tunes C4-DC catabolism in response to the availability of other preferred carbon sources. It attributes DctA a central role in the control of aerobic C4-DC catabolism and suggests a new role to EIIAGlc on transporters (control of substrate uptake by substrate exclusion).
Topics: Aerobiosis; Carbon; Catabolite Repression; Cyclic AMP; Cyclic AMP Receptor Protein; Dicarboxylic Acid Transporters; DNA-Binding Proteins; Escherichia coli; Escherichia coli Proteins; Gene Expression Regulation, Bacterial; Phosphoenolpyruvate Sugar Phosphotransferase System; Promoter Regions, Genetic; Protein Kinases; Signal Transduction; Succinic Acid; Transcription Factors
PubMed: 38432210
DOI: 10.1159/000538095 -
Environmental Research Jun 2024Anaerobically digested sludge supernatant, characterized by its high ammonia and low biodegradable chemical oxygen demand (COD) content, has raised concerns when...
Anaerobically digested sludge supernatant, characterized by its high ammonia and low biodegradable chemical oxygen demand (COD) content, has raised concerns when returned to mainstream treatment lines due to potential impacts on effluent quality. Addressing this, an aerobic granular sludge (AGS) reactor adopted nitritation/denitritation with external COD addition was utilized and achieved a considerable nitrogen treatment capacity of 4.2 kg N/m/d, reaching over 90% removal efficiencies for both ammonia and total inorganic nitrogen. This study applied progressively increased nitrogen loading to select for a microbial community that exhibited high nitrogen oxidation and reduction rates, demonstrating peak rates of 0.5 g N/g VSS/d and 3 g N/g VSS/d, respectively. The enrichment of highly efficient microbial community was achieved along with the increased biomass density peaked at 17 g/L MLVSS, with the system retaining small-sized granular sludge at 0.5 mm. The primary ammonia oxidizing bacteria was Nitrosomonas, while Thauera was the dominated denitrifiers. Quantitative polymerase chain reaction analyses reinforced the enhanced nitrogen removal capacity based on the progressively increased abundance of nitrogen cycling functional genes. The high nitrogen treatment capacity, synergistic attributes of high specific microbial activities and the substantial biomass retention, suggest the AGS's efficacy and capacity in ammonia rich wastewater treatment.
Topics: Bioreactors; Sewage; Ammonia; Nitrogen; Waste Disposal, Fluid; Wastewater; Aerobiosis; Bacteria; Water Pollutants, Chemical
PubMed: 38431070
DOI: 10.1016/j.envres.2024.118573 -
PloS One 2024The activated sludge was collected from the Membrane BioReactor (MBR) pool of the sewage treatment system of Sanxing Town, Jintang County, Chengdu, to obtain a good...
The activated sludge was collected from the Membrane BioReactor (MBR) pool of the sewage treatment system of Sanxing Town, Jintang County, Chengdu, to obtain a good population of heterotrophic nitrifying/aerobic denitrifying (HNAD) bacteria. After undergoing enrichment, isolation, and purification, the HNAD bacteria were selected using the pure culture method. The 16S rDNA molecular technology was used to determine the taxonomy of bacteria. The heterophic nitrifying ability and denitrification capacity of HNAD strains was ascertained through their growth characteristics in heterotrophic nitrification and denitrification media. The results showed that 53 HNAD strains selected from the MBR pool belonged to 2 phyla, 3 classes, 6 orders, 6 families, and 7 genera, with 26 species. Acinetobacter was the largest and dominant genus. Among these, strains numbered (bacterial strain) SW21HD14, SW21HD17, and SW21HD18 were potentially new species in the Acinetobacter genus. Each HNAD strain showed a significant heterotrophic nitrifying and aerobic denitrifying efficiency compared with the control strain (P < 0.05). Specifically, 10 strains demonstrated ammonia nitrogen degradation of greater than 70 mg·L-1 and 9 strains demonstrated nitrate nitrogen degradation above 150 mg·L-1. The HNAD bacteria, which were selected from the MBR pool of sewage treatment system of the Sanxing Town sewage treatment plant, exhibited rich diversity and strong nitrogen removal ability. These findings offered an effective strain source and theoretical basis for implementing biological denitrification technology that involves synchronous nitrification and denitrification.
Topics: Humans; Sewage; Denitrification; Aerobiosis; Nitrification; Bacteria, Aerobic; Bacteria; Heterotrophic Processes; Nitrogen; Nitrites
PubMed: 38236927
DOI: 10.1371/journal.pone.0293136 -
The Science of the Total Environment Feb 2024A naturally occurring multispecies bacterial community composed of Bacillus cereus and two novel bacteria (Microbacterium forte sp. nov. and Stenotrophomonas goyi sp....
A naturally occurring multispecies bacterial community composed of Bacillus cereus and two novel bacteria (Microbacterium forte sp. nov. and Stenotrophomonas goyi sp. nov.) has been identified from a contaminated culture of the microalga Chlamydomonas reinhardtii. When incubated in mannitol- and yeast extract-containing medium, this bacterial community can promote and sustain algal hydrogen production up to 313 mL H·L for 17 days and 163.5 mL H·L for 25 days in high-cell (76.7 μg·mL of initial chlorophyll) and low-cell density (10 μg·mL of initial chlorophyll) algal cultures, respectively. In low-cell density algal cultures, hydrogen production was compatible with algal growth (reaching up to 60 μg·mL of chlorophyll). Among the bacterial community, M. forte sp. nov. was the sole responsible for the improvement in hydrogen production. However, algal growth was not observed in the Chlamydomonas-M. forte sp. nov. consortium during hydrogen-producing conditions (hypoxia), suggesting that the presence of B. cereus and S. goyi sp. nov. could be crucial to support the algal growth during hypoxia. Still, under non‑hydrogen producing conditions (aerobiosis) the Chlamydomonas-M. forte sp. nov. consortium allowed algal growth (up to 40 μg·mL of chlorophyll) and long-term algal viability (>45 days). The genome sequence and growth tests of M. forte sp. nov. have revealed that this bacterium is auxotroph for biotin and thiamine and unable to use sulfate as sulfur source; it requires S-reduced forms such as cysteine and methionine. Cocultures of Chlamydomonas reinhardtii and M. forte sp. nov. established a mutualistic association: the alga complemented the nutrient deficiencies of the bacterium, while the bacterium released ammonium (0.19 mM·day) and acetic acid (0.15 mM·day) for the alga. This work offers a promising avenue for photohydrogen production concomitant with algal biomass generation using nutrients not suitable for mixotrophic algal growth.
Topics: Chlamydomonas reinhardtii; Microbacterium; Chlorophyll; Chlamydomonas; Acetic Acid; Bacteria; Hypoxia; Hydrogen
PubMed: 38159768
DOI: 10.1016/j.scitotenv.2023.169559 -
Bioresource Technology Feb 2024Anticancer drugs are frequently found in domestic wastewater, but knowledge of their impacts on wastewater treatment processes is limited. The effects of three levels of...
Anticancer drugs are frequently found in domestic wastewater, but knowledge of their impacts on wastewater treatment processes is limited. The effects of three levels of concentrations (low, medium, and high) of three anticancer drugs on physicochemical parameters and prokaryotic communities of a continuous-flow aerobic granular sludge (AGS) system were examined. Drugs at medium and high concentrations reduced the removal of total nitrogen and organic matter during the first 15 days of operation by approximately 15-20 % compared to a control, but these effects disappeared afterward. Removal efficiencies of drugs were in the range of 51.2-100 % depending on the concentration level. Drugs at medium and high concentrations reduced the abundance and diversity and altered the composition of prokaryotic communities. Specific taxa were linked to variations in performance parameters after the addition of the drugs. This study provides improved knowledge of the impacts of anticancer drugs in AGS systems operated in continuous-flow reactor.
Topics: Sewage; Waste Disposal, Fluid; Bioreactors; Wastewater; Microbiota; Nitrogen; Aerobiosis
PubMed: 38081471
DOI: 10.1016/j.biortech.2023.130195 -
Ecotoxicology and Environmental Safety Nov 2023High concentration of ammonia poses a common threat to the healthy breeding of marine aquaculture organisms. Since aquaculture water is rich in organic matter,...
High concentration of ammonia poses a common threat to the healthy breeding of marine aquaculture organisms. Since aquaculture water is rich in organic matter, heterotrophic nitrifying bacteria might play a crucial role in ammonia removal. However, their roles in ammonia oxidation remain unknown. Here, we report a novel strain isolated from shrimp aquaculture seawater, identified as Sneathiella aquimaris 216LB-ZA1-12, capable of heterotrophic nitrification. It is the first characterized heterotrophic nitrifier of the order Sneathiellales in the class Alphaproteobacteria. It exhibits high activity in heterotrophic nitrification, removing nearly 94% of ammonium-N under carbon-constrained conditions in 8 days with no observed nitrite accumulation. The heterotrophic nitrification pathway, inferred based on detection and genomic data was as follows: NH→NHOH→NO→NO→NO. While this pathway aligns with the classical nitrification pathway, while the significant difference lies in the absence of classical HAO and HOX encoding genes in the genome, which is common in heterotrophic nitrifying bacteria. In summary, this bacterium is not only valuable for studying the nitrifying mechanism, but also holds potential for practical applications in ammonia removal in marine aquaculture systems and saline wastewater.
Topics: Nitrification; Denitrification; Ammonia; Aerobiosis; Nitrites; Bacteria; Heterotrophic Processes; Aquaculture; Seawater; Alphaproteobacteria; Nitrogen
PubMed: 37839193
DOI: 10.1016/j.ecoenv.2023.115588 -
Microbial Physiology 2024The denitrifying betaproteobacterium Aromatoleum aromaticum EbN1T is a facultative anaerobic degradation specialist and belongs to the environmental bacteria studied... (Review)
Review
The denitrifying betaproteobacterium Aromatoleum aromaticum EbN1T is a facultative anaerobic degradation specialist and belongs to the environmental bacteria studied best on the proteogenomic level. This review summarizes the current state of knowledge about the anaerobic and aerobic degradation (to CO2) of 47 organic growth substrates (23 aromatic, 21 aliphatic, and 3 amino acids) as well as the modes of respiratory energy conservation (denitrification vs. O2-respiration). The constructed catabolic network is comprised of 256 genes, which occupy ∼7.5% of the coding regions of the genome. In total, 219 encoded proteins have been identified by differential proteomics, yielding a proteome coverage of ∼74% of the network. Its degradation section is composed of 31 peripheral and 4 central pathways, with several peripheral modules (e.g., for 4-ethylphenol, 2-phenylethylamine, indoleacetate, and phenylpropanoids) discovered only after the complete genome [Arch Microbiol. 2005 Jan;183(1):27-36] and a first proteomic survey [Proteomics. 2007 Jun;7(13):2222-39] of A. aromaticum EbN1T were reported. The activation of recalcitrant aromatic compounds involves a suite of biochemically intriguing reactions ranging from C-H-bond activation (e.g., ethylbenzene dehydrogenase) via carboxylation (e.g., acetophenone carboxylase) to oxidative deamination (e.g., benzylamine), reductive dearomatization (benzoyl-CoA), and epoxide-forming oxygenases (e.g., phenylacetyl-CoA). The peripheral reaction sequences are substrate-specifically induced, mediated by specific transcriptional regulators with in vivo response thresholds in the nanomolar range. While lipophilic substrates (e.g., phenolics) enter the cells via passive diffusion, polar ones require active uptake that is driven by specific transporters. Next to the protein repertoire for canonical complexes I-III, denitrification, and O2-respiration (low- and high-affinity oxidases), the genome encodes an Ndh-II, a tetrathionate reductase, two ETF:quinone oxidoreductases, and two Rnf-type complexes, broadening the electron transfer flexibility of the strain. Taken together, the detailed catabolic network presented here forms a solid basis for future systems biology-level studies with A. aromaticum EbN1T.
Topics: Bacterial Proteins; Anaerobiosis; Metabolic Networks and Pathways; Aerobiosis; Proteome; Proteomics; Denitrification; Rhodocyclaceae
PubMed: 37816339
DOI: 10.1159/000534425 -
Foods (Basel, Switzerland) Sep 2023The aim of this study was to assess the antimicrobial effects of myrtle ( L.) essential oil (EO) on pathogenic ( O157:H7 NCTC 12900; Listeria monocytogenes ATCC BAA-679)...
The aim of this study was to assess the antimicrobial effects of myrtle ( L.) essential oil (EO) on pathogenic ( O157:H7 NCTC 12900; Listeria monocytogenes ATCC BAA-679) and spoilage microbiota in beef and determine its minimum inhibitory concentration (MIC) and antioxidant activity. The behavior of LAB, Enterobacteriaceae, spp., and fungi, as well as total mesophilic (TM) and total psychotropic (TP) counts, in beef samples, was analyzed during storage at 2 and 8 °C in two different packaging systems (aerobiosis and vacuum). Leaves of myrtle were dried, its EO was extracted by hydrodistillation using a Clevenger-type apparatus, and the chemical composition was determined using chromatographical techniques. The major compounds obtained were myrtenyl acetate (15.5%), β-linalool (12.3%), 1,8-cineole (eucalyptol; 9.9%), geranyl acetate (7.4%), limonene (6.2%), α-pinene (4.4%), linalyl o-aminobenzoate (5.8%), α-terpineol (2.7%), and myrtenol (1.2%). Myrtle EO presented a MIC of 25 µL/mL for O157:H7 NCTC 12900, , ATCC BAA-679, Enterobacteriaceae, and O157:H7 ATCC 35150 and 50µL/mL for spp. The samples packed in aerobiosis had higher counts of deteriorative microorganisms than samples packed under vacuum, and samples with myrtle EO presented the lowest microbial contents, indicating good antimicrobial activity in beef samples. Myrtle EO is a viable natural alternative to eliminate or reduce the pathogenic and deteriorative microorganisms of meat, preventing their growth and enhancing meat safety.
PubMed: 37761099
DOI: 10.3390/foods12183390 -
Microbiology Spectrum Sep 2023Quaternary ammonium compounds (QACs) have been extensively used in the community, healthcare facilities, and food chain, in concentrations between 20 and 30,000 mg/L....
Quaternary ammonium compounds (QACs) have been extensively used in the community, healthcare facilities, and food chain, in concentrations between 20 and 30,000 mg/L. and are ubiquitous in these settings and are recognized as nosocomial pathogens worldwide, but QACs' activity against strains from diverse epidemiological and genomic backgrounds remained largely unexplored. We evaluated the role of isolates from different sources, years, and clonal lineages as hosts of QACs tolerance genes and their susceptibility to QACs in optimal, single-stress and cross-stress growth conditions. Only 1% of the isolates included in this study and 0.5% of publicly available genomes carried or genes, shared with >60 species of Bacillota, Pseudomonadota, Actinomycetota, or Spirochaetota. These genes were generally found within close proximity of antibiotics and/or metals resistance genes. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of benzalkonium chloride (BC) and didecyldimethylammonium chloride ranged between 0.5 and 4 mg/L (microdilution: 37°C/20 h/pH = 7/aerobiosis) for 210 and isolates (two isolates carrying ). Modified growth conditions (e.g., 22°C/pH = 5) increased MIC/MBC (maximum of eightfold and MBC = 16 mg/L) and changed bacterial growth kinetics under BC toward later stationary phases in both species, including in isolates without QACs tolerance genes. In conclusion, are susceptible to in-use QACs concentrations and rarely carry QACs tolerance genes. However, their potential gene exchange with different microbiota, the decreased susceptibility to QACs under specific environmental conditions, and the presence of subinhibitory QACs concentrations in various settings may contribute to the selection of particular strains and, thus, require a One Health strategy to maintain QACs effectiveness. IMPORTANCE Despite the increasing use of quaternary ammonium compounds (QACs), the susceptibility of pathogens to these antimicrobials remains largely unknown. and are susceptible to in-use QACs concentrations and are not main hosts of QACs tolerance genes but participate in gene transfer pathways with diverse bacterial taxa exposed to these biocides. Moreover, QACs tolerance genes often share the same genetic contexts with antibiotics and/or metals resistance genes, raising concerns about potential co-selection events. and showed increased tolerance to benzalkonium chloride under specific environmental conditions (22°C, pH = 5), suggesting that strains might be selected in settings where they occur along with subinhibitory QACs concentrations. Transcriptomic studies investigating the cellular mechanisms of adaptation to QACs tolerance, along with longitudinal metadata analysis of tolerant populations dynamics under the influence of diverse environmental factors, are essential and should be prioritized within a One Health strategy.
PubMed: 37737589
DOI: 10.1128/spectrum.02324-23