Microplastics (MPs) are emerging pollutants as vectors for microbial colonization, but their role as nutrients sources for microbial communities has rarely been reported. This study explored the ...impact of six types of MPs on assimilable organic carbon (AOC) and microbial communities over eight weeks. The following were the primary conclusions: (1) MPs contributed to AOC increment and subsequently increased bacterial regrowth potential. The maximum AOC reached 722.03 μg/L. The increase in AOC formation corresponded to AOC NOX, except in PVC samples where AOC P17 primarily increased. (2) The MPs accelerated bacterial growth and changed the bacterial distribution between the biofilm and water phases. A high MP surface-area-to-volume ratio or low MPs density contributed to bacterial accumulation and biofilm formation around the plastisphere, thereby decreasing the relative microbial proportion in the water phase. (3) High-throughput sequencing and scanning electron microscope revealed that different MPs shaped various microbial communities temporally and spatially. (4) Biofilm formatting and formatted models were established and simulated to explain the kinetic interaction between the AOC and bacteria inhabiting the plastisphere. Finally, the challenges that plastic-deprived AOC represent in terms of anti-bacterial measures and chemical safety are discussed.
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•The nutrient-supply effect of microplastics for bacterial growth was explored.•Different MPs contribute various assimilable organic carbon formation and subsequently shaped microbial communities.•MPs’ properties have impacts on bacterial growth and distribution between biofilm and water phase.•Biofilm formatting and formatted phases of biofilm, were defined and simulated.
Our intestinal microbiota harbours a diverse bacterial community required for our health, sustenance and wellbeing. Intestinal colonization begins at birth and climaxes with the acquisition of two ...dominant groups of strict anaerobic bacteria belonging to the Firmicutes and Bacteroidetes phyla. Culture-independent, genomic approaches have transformed our understanding of the role of the human microbiome in health and many diseases. However, owing to the prevailing perception that our indigenous bacteria are largely recalcitrant to culture, many of their functions and phenotypes remain unknown. Here we describe a novel workflow based on targeted phenotypic culturing linked to large-scale whole-genome sequencing, phylogenetic analysis and computational modelling that demonstrates that a substantial proportion of the intestinal bacteria are culturable. Applying this approach to healthy individuals, we isolated 137 bacterial species from characterized and candidate novel families, genera and species that were archived as pure cultures. Whole-genome and metagenomic sequencing, combined with computational and phenotypic analysis, suggests that at least 50-60% of the bacterial genera from the intestinal microbiota of a healthy individual produce resilient spores, specialized for host-to-host transmission. Our approach unlocks the human intestinal microbiota for phenotypic analysis and reveals how a marked proportion of oxygen-sensitive intestinal bacteria can be transmitted between individuals, affecting microbiota heritability.
This study aimed to determine the effect of aerobic and anaerobic incubation, and the addition of CaCO₃ on the growth and antibacterial activity of Lactic Acid Bacteria (LAB) isolated from laying ...hens’ intestines (strain ISA Brown) after given 4% AKBISprob. The LAB used in this study was the isolates strains that produced the strongest antibacterial activity with inhibition zone ≥ 5 mm. The treatments consisted of two incubations condition (aerobic and anaerobic) with five concentrations of CaCO3 (1%, 2%, 3%, 4%, and 5%). Each treatment consisted of three repetitions. Total Plate Count (TPC) method and the agar diffusion method were used to calculate the amount of LAB and antibacterial activity, respectively. The results showed that anaerobic conditions had a significant effect (P0.05) on the increase of LAB growth, but both of aerobic and anaerobic conditions (P0.05) did not show significant effect on antibacterial activity. The addition of CaCO3 had a significant effect (P0.05) on the increase in growth and antibacterial activity of LAB. Based on the results of the study, it can be concluded that anaerobic incubation can increase the growth of two isolate of LAB isolates (P31S72 and P31H62), however aerobic and anaerobic incubation have no effect on antibacterial activity. In addition, the administration of 3% CaCO3 can increase the growth and antibacterial activity of all LAB isolates.
Bacteria will accompany humans in our exploration of space, making it of importance to study their adaptation to the microgravity environment. To investigate potential phenotypic changes for bacteria ...grown in space,
was cultured onboard the International Space Station with matched controls on Earth. Samples were challenged with different concentrations of gentamicin sulfate to study the role of drug concentration on the dependent variables in the space environment. Analyses included assessments of final cell count, cell size, cell envelope thickness, cell ultrastructure, and culture morphology. A 13-fold increase in final cell count was observed in space with respect to the ground controls and the space flight cells were able to grow in the presence of normally inhibitory levels of gentamicin sulfate. Contrast light microscopy and focused ion beam/scanning electron microscopy showed that, on average, cells in space were 37% of the volume of their matched controls, which may alter the rate of molecule-cell interactions in a diffusion-limited mass transport regime as is expected to occur in microgravity. TEM imagery showed an increase in cell envelope thickness of between 25 and 43% in space with respect to the Earth control group. Outer membrane vesicles were observed on the spaceflight samples, but not on the Earth cultures. While
suspension cultures on Earth were homogenously distributed throughout the liquid medium, in space they tended to form a cluster, leaving the surrounding medium visibly clear of cells. This cell aggregation behavior may be associated with enhanced biofilm formation observed in other spaceflight experiments.
The monitoring of life of microbial populations is of the uttermost importance in environmental and food analysis, agriculture, as well as in medicine. The duration of bacteria adaptation to new ...environmental conditions, its lifetime and the divisions’ pace are the key information in many studies. It was found that the fully-mechanized flow analysis system based on solenoid valves and pumps, paired with a dedicated flow-through optoelectronic detector can be successfully applied for monitoring of bacteria growth. The applicability of the designed multicommutated flow analysis (MCFA) system was proved by analysis of solutions containing bacteria cells proceeded by tests of McFarland (McF) standards. The developed setup allowed modelling and simulation of microbial growth, as well as monitoring of the bacteria growth in real-time manner to be carried out. The monitor is useful for the quantitative estimation of the basic parameters of bacteria population like its size, the rate of bacteria multiplication, as well as the times of lag, log and stationary phases of microbial growth.
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•Optoelectronic detector of microbial population size is developed.•The detector is used in microprocessor-controlled flow analysis system.•The system plays the role of real-time-operating monitor of bacterial growth.•The monitor allows the quantitative parameters of bacterial growth to be estimated.
Oral streptococci are considered as an opportunistic pathogen associated with initiation and progression of various oral diseases. However, since the currently-available treatments often accompany ...adverse effects, alternative strategy is demanded to control streptococci. In the current study, we investigated whether short-chain fatty acids (SCFAs), including sodium acetate (NaA), sodium propionate (NaP), and sodium butyrate (NaB), can inhibit the growth of oral streptococci. Among the tested SCFAs, NaP most potently inhibited the growth of laboratory and clinically isolated strains of Streptococcus gordonii under anaerobic culture conditions. However, the growth inhibitory effect of NaP on six different species of other oral streptococci was different depending on their culture conditions. Metabolic changes such as alteration of methionine biosynthesis can affect bacterial growth. Indeed, NaP enhanced intracellular methionine levels of oral streptococci as well as the mRNA expression level of methionine biosynthesis-related genes. Collectively, these results suggest that NaP has an inhibitory effect on the growth of oral streptococci, which might be due to alteration of methionine biosynthesis. Thus, NaP can be used an effective bacteriostatic agent for the prevention of oral infectious diseases caused by oral streptococci.
Many studies have used the relative activities of extracellular enzymes associated with microbial carbon (C), nitrogen (N) and phosphorus (P) acquisition to infer the relative C vs. nutrient ...limitation of the microbial community. However, recent experimental and theoretical evidence has shown that the use of ecoenzymatic ratio to infer limiting microbial resources may be invalid. We added the two contrasting leaf litters ash (Fraxinus excelsior L., relatively more labile and nutrient rich) and oak (Quercus robur L.), into samples of mineral soils to validate the use of ecoenzymatic stoichiometry to reflect microbial resource limitation. The litter treatments were also combined with N and P addition treatments to push microbial communities toward stronger C limitation. The microbial resource limitations were examined in all treatments by the responses in microbial respiration, bacterial and fungal growth, microbial community composition, and by detecting the responses of microbial growth to factorial C and nutrient additions in short-term limiting factor assays (LFAs). High ratios of β-1,4-glucosidase (BG) to β-1,4-N-acetylglucosaminidase (NAG) + leucine aminopeptidase (LAP) (>2:1) contrasted with the expected reduction in C limitation after initial litter inputs. The high ratio was mainly driven by an increase in BG activity associated with high energy supply and high microbial rates of metabolism induced by added labile C substrates. During the later incubation period (7–56 days), decreasing respiration and bacterial and fungal growth rates reflected increased microbial C limitation in all treatments. An increasing BG/(NAG + LAP) ratio was in line with increasing microbial C limitation in the ash treatment where cellulose dominated as microbial C source, but a decreasing BG/(NAG + LAP) ratio was inconsistent with the temporal dynamics in microbial C limitation in the oak treatment where substrates other than cellulose (i.e., microbial necromass and lignin) dominated as C source late in the incubation. The increased BG/(NAG + LAP) ratio was in line with intensified microbial C limitation by NP addition, which was mainly due to the stimulated BG activity. In the oak and litter plus NP treatments, fungal growth was stimulated and NAG - an enzyme targeting amino sugars - was increased, presumably to meet the fungal C demand by utilizing microbial necromass - partly consisting of amino sugar polymers. Taken together, these results suggest that variation in substrate quality, availability and how these matched the present microbial energy allocation strategy and resource allocation to enzyme production caused a substantial variation in the BG/(NAG + LAP) ratio, thereby disconnecting the ratio from unambiguously reflecting the microbial resource limitation.
•Ecoenzymatic stoichiometry hypothesis was tested by several experiments.•The BG/(NAG + LAP) ratios contrasted with microbial C limitation after litter inputs.•Increasing microbial C limitation induces higher BG/(NAG + LAP) ratios in labile litter.•Increasing microbial C limitation induces lower BG/(NAG + LAP) ratios in recalcitrant litter.•Ecoenzymatic ratios can capture microbial C limitation induced by NP addition.
In response to the low efficiency of the anaerobic digestion (AD) process in generating methane gas, we apply for the first time the use of coated/Fe0 with Mg(OH)2 to enhance the production rate of ...methane gas from the degradation of waste sludge. A series of batch tests investigated several operations factors followed by a semi-continuous operation system examined the long-term production of methane gas in the presence of the coated/Fe0 were performed. The coating ratio of Mg(OH)2/Fe0 and the dosage of coated/Fe0 were optimized to acquire the highest production rate of methane as 0.5% and 25mg/gVS, respectively. Under these optimum conditions, the methane production increased by 46.6% in the batch tests and 120% in the semi-continuous operation system compared to the control reactor. The results revealed that both Fe0 and Mg(OH)2 did not significantly improve the production of methane when each one was used alone at different dosages, and the improved methane production originated from the synergetic effect of combining these two materials. The crucial role of Mg(OH)2 coating layer was associated with the controlled reactivity release of Fe0, which was indicated by the slow release of Fe2+ and Fe3+ in the bioreactors. Furthermore, the addition of coated/Fe0 stimulated bacterial growth, increased methane content, and maintained the pH within the optimum range in the bioreactors. The dosing time of coated/Fe0 was investigated during the four stages of AD process, and the best dosing time was found in the methanogenic stage (on Day 4). Overall, based on the experimental and predicted methane production, the coated/Fe0 has a great potential for the practical applications of AD.
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•The highest CH4 production was observed at the optimum coating ratio of 0.5 (Mg/Fe0:0.5).•The coated/Fe0 enhanced biogas and CH4 production by 95 and 120%, respectively.•The coated/Fe0 enhanced CH4 production at different pH values (3–11).•The coated/Fe0 significantly improved the bulk growth of bacteria in the digesters.
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