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Microbiological Research May 2023Corn straw is suitable for preservation as silage despite being neglected due to its varying chemical composition, yield, and pathogenic influence during ensiling. This...
Corn straw is suitable for preservation as silage despite being neglected due to its varying chemical composition, yield, and pathogenic influence during ensiling. This study examined the effects of beneficial organic acid-producing lactic acid bacteria (LAB), including Lactobacillus buchneri (Lb), L. plantarum (Lp), or their combination (LpLb), on fermentation profile, aerobic stability, and microbial community dynamics of corn straw harvested at late maturity stage after 7d, 14d, 30d, and 60d of ensiling. Higher levels of beneficial organic acids, LAB counts, and crude protein (CP), and lower levels of pH and ammonia nitrogen were detected in LpLb-treated silages after 60d. Lactobacillus, Candida, and Issatchenkia abundances were higher (P < 0.05) in Lb and LpLb-treated corn straw silages after 30d and 60d ensiling. Additionally, the positive correlation between Lactobacillus, Lactococcus and Pediococcus, and the negative correlation with Acinetobacter in LpLb-treated silages after 60d emphasizes a potent interaction mechanism initiated by organic acid and composite metabolite production to reduce pathogenic microorganisms' growth. Also, a significant correlation between Lb and LpLb-treated silages with CP and neutral detergent fiber after 60d further highlights the synergistic effect of incorporating L. buchneri and L. plantarum for improved nutritional components of mature silages. The combination of L. buchneri and L. plantarum improved aerobic stability, fermentation quality, and bacterial community and reduced fungal population after 60d of ensiling, which are properties of well-preserved corn straw.
Topics: Lactobacillus plantarum; Zea mays; Fermentation; Lactobacillus; Microbiota; Aerobiosis
PubMed: 36812838
DOI: 10.1016/j.micres.2023.127329 -
Microbiology Spectrum Feb 2023The ability of a foodborne pathogen to tolerate environmental stress critically affects food safety by increasing the risk of pathogen survival and transmission in the...
The ability of a foodborne pathogen to tolerate environmental stress critically affects food safety by increasing the risk of pathogen survival and transmission in the food supply chain. Campylobacter jejuni, a leading bacterial cause of foodborne illnesses, is an obligate microaerophile and is sensitive to atmospheric levels of oxygen. Currently, the molecular mechanisms of how C. jejuni withstands oxygen toxicity under aerobic conditions have not yet been fully elucidated. Here, we show that when exposed to aerobic conditions, C. jejuni develops a thick layer of bacterial capsules, which in turn protect C. jejuni under aerobic conditions. The presence of both capsular polysaccharides and lipooligosaccharides is required to protect C. jejuni from excess oxygen in oxygen-rich environments by alleviating oxidative stress. Under aerobic conditions, C. jejuni undergoes substantial transcriptomic changes, particularly in the genes of carbon metabolisms involved in amino acid uptake, the tricarboxylic acid (TCA) cycle, and the Embden-Meyerhof-Parnas (EMP) pathway despite the inability of C. jejuni to grow aerobically. Moreover, the stimulation of carbon metabolism by aerobiosis increases the level of glucose-6-phosphate, the EMP pathway intermediate required for the synthesis of surface polysaccharides. The disruption of the TCA cycle eliminates aerobiosis-mediated stimulation of surface polysaccharide production and markedly compromises aerotolerance in C. jejuni. These results in this study provide novel insights into how an oxygen-sensitive microaerophilic pathogen survives in oxygen-rich environments by adapting its metabolism and physiology. Oxygen-sensitive foodborne pathogens must withstand oxygen toxicity in aerobic environments during transmission to humans. C. jejuni is a major cause of gastroenteritis, accounting for 400 million to 500 million infection cases worldwide per year. As an obligate microaerophile, C. jejuni is sensitive to air-level oxygen. However, it has not been fully explained how this oxygen-sensitive zoonotic pathogen survives in aerobic environments and is transmitted to humans. Here, we show that under aerobic conditions, C. jejuni boosts its carbon metabolism to produce a thick layer of bacterial capsules, which in turn act as a protective barrier conferring aerotolerance. The new findings in this study improve our understanding of how oxygen-sensitive C. jejuni can survive in aerobic environments.
PubMed: 36786626
DOI: 10.1128/spectrum.03761-22 -
Journal of Agricultural and Food... Feb 2023While plant-specialized metabolites can affect mammal health, their fate during the aerobic deterioration of crop silage remains poorly understood. In this study, we...
While plant-specialized metabolites can affect mammal health, their fate during the aerobic deterioration of crop silage remains poorly understood. In this study, we investigated the metabolization of benzoxazinoids (BXs) in silages of two maize genotypes (W22 wild type and mutant line) during aerobic deterioration. In W22 plants, concentrations of the aglucone BXs DIMBOA and HMBOA in silage decreased over time upon air exposure, while concentrations of MBOA and BOA increased. Mutant plants had low levels of BXs, which did not significantly vary over time. Aerobic stability was BX-dependent, as pH and counts of yeasts and molds were higher in W22 compared to that in silage. The nutrient composition was not affected by BXs. These preliminary results may be used to estimate the amounts of BXs provided to farm animals via silage feeding. However, further research is warranted under different harvest and storage conditions.
Topics: Animals; Zea mays; Silage; Benzoxazines; Fungi; Yeasts; Fermentation; Aerobiosis; Mammals
PubMed: 36692976
DOI: 10.1021/acs.jafc.2c06699 -
Applied and Environmental Microbiology Feb 2023Psychrophilic bacteria with aerobic denitrification ability have promising potential for application in nitrogen-contaminated wastewater treatment, especially under cold...
Psychrophilic bacteria with aerobic denitrification ability have promising potential for application in nitrogen-contaminated wastewater treatment, especially under cold conditions. A better understanding of the cold adaptation mechanism during aerobic denitrification would be beneficial for the practical application of this type of functional bacterium. In this study, Bacillus simplex H-b with good denitrification performance at 5°C was used to investigate the corresponding cold tolerance mechanism. Transcriptomics and nitrogen removal characterization experiments were conducted at different temperatures (5°C, 20°C, and 30°C). At low temperatures, more nitrogen was utilized for assimilation, accompanied by the accumulation of ATP and extracellular polymeric substances (EPS), rather than transforming inorganic nitrogen in the dissimilation pathway. In addition, the proportion of unsaturated fatty acids was higher in strains cultured at low temperatures. At the molecular level, the adjustment of membrane transport, synthesis of cofactors and vitamins, and transcriptional regulators might contribute to the survival of the strain under cold conditions. Moreover, nucleotide precursor synthesis, translation, and oxidative and temperature stress response mechanisms also enhanced the resistance of strain H-b to low temperatures. The results suggest that combining multiple regulatory mechanisms and synergistic adaptation to cold stress enabled the growth and relatively high nitrogen removal rate (27.22%) of strain H-b at 5°C. By clarifying the mechanism of regulation and cold resistance of strain H-b, a theoretical foundation for enhancing the application potential of this functional bacterium for nitrogen-contaminated wastewater treatment was provided. The newly isolated aerobic denitrifying bacterium Bacillus simplex H-b removed various forms of inorganic nitrogen (nitrate, nitrite, and ammonium) from wastewater, even when the temperature was as low as 5°C. Although this environmentally functional bacterium has been suggested as a promising candidate for nitrogen-contaminated water treatment at low temperatures, understanding its cold adaptation mechanism during aerobic denitrification is limited. In this study, the cold tolerance mechanism of this strain was comprehensively explained. Furthermore, a theoretical basis for the practical application of this type of functional bacterium for nitrogen removal in cold regions is provided. The study expands our understanding of the survival strategy of psychrophilic bacteria and hence supports their further utilization in wastewater treatment applications.
Topics: Denitrification; Nitrification; Aerobiosis; Nitrites; Nitrates; Bacteria; Nitrogen; Heterotrophic Processes
PubMed: 36656033
DOI: 10.1128/aem.01928-22 -
Nature Microbiology Jan 2023Chlamydiae is a bacterial phylum composed of obligate animal and protist endosymbionts. However, other members of the Planctomycetes-Verrucomicrobia-Chlamydiae...
Chlamydiae is a bacterial phylum composed of obligate animal and protist endosymbionts. However, other members of the Planctomycetes-Verrucomicrobia-Chlamydiae superphylum are primarily free living. How Chlamydiae transitioned to an endosymbiotic lifestyle is still largely unresolved. Here we reconstructed Planctomycetes-Verrucomicrobia-Chlamydiae species relationships and modelled superphylum genome evolution. Gene content reconstruction from 11,996 gene families suggests a motile and facultatively anaerobic last common Chlamydiae ancestor that had already gained characteristic endosymbiont genes. Counter to expectations for genome streamlining in strict endosymbionts, we detected substantial gene gain within Chlamydiae. We found that divergence in energy metabolism and aerobiosis observed in extant lineages emerged later during chlamydial evolution. In particular, metabolic and aerobic genes characteristic of the more metabolically versatile protist-infecting chlamydiae were gained, such as respiratory chain complexes. Our results show that metabolic complexity can increase during endosymbiont evolution, adding an additional perspective for understanding symbiont evolutionary trajectories across the tree of life.
Topics: Animals; Bacteria; Chlamydia
PubMed: 36604515
DOI: 10.1038/s41564-022-01284-9 -
Scientific Reports Dec 2022Aerobic granular sludge (AGS) is a proven resource for the recovery of biopolymers like alginate-like polymers (ALP). This is the first report on the dynamics of ALP...
Aerobic granular sludge (AGS) is a proven resource for the recovery of biopolymers like alginate-like polymers (ALP). This is the first report on the dynamics of ALP produced by AGS (ALP-AGS) in a full-scale wastewater treatment plant (WWTP), optimization of ALP recovery from AGS, and adsorption of cadmium (Cd) by ALP. Recovery of ALP was highest when using 120 mL of 0.2 M NaCO at 70 °C for 45 min. Seasonal (1.5 years, over 3100 cycles) and intra-cycle changes in ALP-AGS in the WWTP were monitored. The ALP content in AGS increased in the transition period between winter and spring, reaching over 150 mg/g MLSS. In the batch reactor cycle, the ALP-AGS level peaked 2 h after the start of aeration (mean peak level: 120 mg/g MLSS), then decreased about two-fold by the end of the cycle. The ALP-AGS had a small surface area and a lamellar structure with crystalline outgrowths. The optimal conditions of Cd adsorption with ALP were a dosage of 7.9 g d.m./L, a pH of 4-8, and an equilibrium time of 60 min. Carboxyl and hydroxyl groups were the key functional groups involved in Cd adsorption. According to the Sips model, the maximum Cd adsorption capacity of ALP-AGS was 29.5 mg/g d.m., which is similar to that of commercial alginate. AGS is a richer source of ALP than activated sludge, which ensures the cost-effectiveness of ALP recovery and increases the sustainability of wastewater treatment. Information on the chemical properties and yields of ALP from full-scale WWTPs is important for downstream applications with the recovered ALP.
Topics: Sewage; Wastewater; Cadmium; Waste Disposal, Fluid; Polymers; Alginates; Adsorption; Bioreactors; Aerobiosis
PubMed: 36564508
DOI: 10.1038/s41598-022-26743-5 -
International Journal of Environmental... Nov 2022Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. AGS formation belongs to microbial self-aggregation. Investigation of the formation and...
Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. AGS formation belongs to microbial self-aggregation. Investigation of the formation and stability of AGS is widely paid attention to, in particular the structure stability of large size granules. Two types of AGS were developed in two sequencing batch reactors fed by two different wastewaters, respectively. Through confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM), the structure and composition of granules were analyzed. Filamentous bacteria were observed in granules from synthetic wastewater reactor, while filamentous bacteria and stalked ciliates ( sp.) were simultaneously found in granules from domestic wastewater reactor. The analytic results show that filamentous bacteria and stalked ciliates acting as skeletons play important roles in the formation and stability of granules. With the bonding of extracellular polymeric substances (EPS), the filamentous bacteria and stalked ciliates could build bridges and frames to promote the aggregation of bacteria; these microorganisms could create a space grid structure around the surface layer of granules to enhance the strength of granules, and the remnants of the stalks could serve as supports to fix the steadiness of granules.
Topics: Sewage; Wastewater; Waste Disposal, Fluid; Bioreactors; Aerobiosis; Bacteria
PubMed: 36497821
DOI: 10.3390/ijerph192315747 -
Microorganisms Nov 2022γ-aminobutyric acid (GABA) has several beneficial effects on human health. GABA may be produced via chemical synthesis or through microbial metabolism, and is...
γ-aminobutyric acid (GABA) has several beneficial effects on human health. GABA may be produced via chemical synthesis or through microbial metabolism, and is recognized as a GABA-producing species. In this study, 11 strains were screened for GABA production, and the best producers were selected to verify the effect of aerobic (AE) and respiratory (RS) cultivations on growth parameters, biomass, and GABA accumulation. LB12 was then used to evaluate the combined effect of the incubation atmosphere (anaerobiosis vs. aerobiosis), cell protection (free vs. immobilized cells), and cell recycling (fresh vs. starved cells) on GABA production. Glutamate (GLU) consumption and GABA accumulation were detected by Thin-layer Chromatography (TLC) and RP-HPLC analyses. The ability to produce GABA was widespread among the strains. AE and RS growth improved biomass production, but oxygen availability impaired GLU to GABA conversion, and the anaerobically growing cells had the highest GABA productivity. Immobilized strains had lower efficiency in both GLU uptake and conversion compared to free cells, probably due to the poor diffusion in alginate beads. The use of resting cells allowed further GABA production without the cultivation step, but cell activity was exhausted after three cycles of reutilization. LB12 is an excellent GABA producer, and AE cultivation can be exploited to improve the final cell density; however, the conditions for boosting GLU to GABA conversion and cell regeneration need to be further investigated.
PubMed: 36363776
DOI: 10.3390/microorganisms10112184 -
Brazilian Journal of Microbiology :... Dec 2022A 1-year-old female mixed-breed cat was admitted to a veterinary hospital in Southern Brazil with tachypnea, low thoracic amplitude, restrictive breathing pattern, and...
A 1-year-old female mixed-breed cat was admitted to a veterinary hospital in Southern Brazil with tachypnea, low thoracic amplitude, restrictive breathing pattern, and cyanotic mucous membranes 2 days after elective castration surgery. Radiography revealed pleural effusion, and approximately 100-200 mL of fluid was collected by thoracocentesis. The reddish purulent exudate contained large numbers of yellowish-white granules with branched filamentous structures on cytological examination. The fluid was plated on blood agar and incubated under aerobiosis at 37 °C. On the third day of incubation, circular, dry, and opaque colonies, measuring < 0.5 mm in diameter, were observed. Their phenotypic and molecular characteristics were compatible with Buchananella hordeovulneris (basonym: Actinomyces hordeovulneris), a pathogenic actinomycete rarely detected in cats. Our findings indicate that B. hordeovulneris should be included in the differential diagnosis of pyothorax in cats together with Actinomyces spp. and Nocardia spp. Taxonomic confirmation of disease-causing microorganisms in animals is important to understand the course of infection and its association with disease epidemiology.
Topics: Female; Cats; Animals; Actinomyces; Empyema, Pleural; Brazil; Cat Diseases
PubMed: 36242745
DOI: 10.1007/s42770-022-00845-8 -
Journal of Animal Science Nov 2022For baled silages, production of clostridial fermentation products can be exacerbated by exceeding normal moisture targets (45% to 55%), and/or by the application of...
Nutritive value, silage fermentation characteristics, and aerobic stability of grass-legume round-baled silages at differing moisture concentrations with and without manure fertilization and microbial inoculation.
For baled silages, production of clostridial fermentation products can be exacerbated by exceeding normal moisture targets (45% to 55%), and/or by the application of dairy slurry before harvest. Our objectives were to test a microbial inoculant as a mitigant of clostridial products in high-moisture, grass-legume (52% ± 13.8% cool-season grasses, 44.0% ± 14.0% legumes [predominately alfalfa]) baled silages in swards that were fertilized with dairy slurry. A secondary objective was to examine the effects of bale moisture and inoculation on the aerobic stability of these fermented silages following exposure to air. After the first-cutting was removed, three manure treatments were applied as a whole-plot factor: 1) control (no manure); 2) slurry applied immediately to stubble (63,250 L/ha); or 3) slurry applied after a 1-wk delay (57,484 L/ha). An interactive arrangement of bale moisture (64.1% or 48.4%) and inoculation (yes or no) served as a subplot term in the experiment. The inoculant contained both homolactic (Lactococcus lactis 0224) and heterolactic (Lactobacillus buchneri LB1819) bacteria. The experimental design was analyzed as a randomized complete block with four replications, and the study included 48 experimental units (1.2 × 1.2-m round bales). Total fermentation acids were affected (P ≤ 0.021) by slurry application strategies, but this was likely related to inconsistent bale moisture across slurry-application treatments. Concentrations of butyric acid were low, and there were no detectable contrasts comparing manure treatments (mean = 0.05%; P ≥ 0.645). Bale moisture affected all measures of fermentation, with bales made at 64.1% moisture exhibiting a more acidic final pH (4.39 vs. 4.63; P < 0.001), less residual water-soluble carbohydrates (2.1% vs. 5.1%; P < 0.001), as well as greater lactic acid (4.64% vs. 2.46%; P < 0.001), acetic acid (2.26% vs. 1.32%; P < 0.001), and total fermentation acids (7.37% vs. 3.97%; P < 0.001). Inoculation also reduced pH (4.47 vs. 4.56; P = 0.029), and increased acetic acid (1.97% vs. 1.61%; P < 0.001) and 1,2-propanediol (1.09% vs. 0.72%; P < 0.001) compared to controls. During a 34-d aerobic exposure period, maximum surface bale temperatures were not affected (P ≥ 0.186) by any aspect of treatment, likely due to the prevailing cool ambient temperatures; however, yeast counts were numerically lower in response to greater (P < 0.001) production of acetic acid that was stimulated by both high bale moisture and inoculation.
Topics: Animals; Silage; Fermentation; Poaceae; Manure; Nutritive Value; Medicago sativa; Vegetables; Acetic Acid; Fertilization; Zea mays; Aerobiosis
PubMed: 36205250
DOI: 10.1093/jas/skac325