Identification of plastic-degrading bacteria in the human gut.

Environmental pollution caused by the excessive use of plastics has resulted in the inflow of microplastics into the human body. However, the effects of microplastics on the human gut microbiota still need to be better understood. To determine whether plastic-degrading bacteria exist in the human gut, we collected the feces of six human individuals, did enrichment cultures and screened for bacterial species with a low-density polyethylene (LDPE) or polypropylene (PP)-degrading activity using a micro-spray method. We successfully isolated four bacterial species with an LDPE-degrading activity and three with a PP-degrading activity. Notably, all bacterial species identified with an LDPE or PP-degrading activity were opportunistic pathogens. We analyzed the microbial degradation of the LDPE or PP surface using scanning electron microscopy and confirmed that each bacterial species caused the physical changes. Chemical structural changes were further investigated using X-ray photoelectron spectroscopy and Fourier-transform-infrared spectroscopy, confirming the oxidation of the LDPE or PP surface with the formation of carbonyl groups (C=O), ester groups (CO), and hydroxyl groups (-OH) by each bacterial species. Finally, high temperature gel permeation chromatography (HT-GPC) analysis showed that these bacterial species performed to a limited extent depolymerization. These results indicate that, as a single species, these opportunistic pathogens in the human gut have a complete set of enzymes and other components required to initiate the oxidation of the carbon chains of LDPE or PP and to degrade them. Furthermore, these findings suggest that these bacterial species can potentially biodegrade and metabolize microplastics in the human gut.

Biodegradation of polyvinyl chloride by Citrobacter koseri isolated from superworms (Zophobas atratus larvae).

Polyvinyl chloride (PVC) is one of the widely used plastic products worldwide, and its accumulation in the natural environment has become a major global issue with regard to the environment and biotic health. There is accordingly strong demand for the development of solutions and methods for environmental remediation. Degrading plastic waste using microorganisms is an effective and eco-friendly method. However, evidence of bacteria that afford efficient biodegradation of unplasticized, pure PVC film has yet to be reported. Therefore, the biodegradation of PVC becomes very important. Here, we present results on the physicochemical and structural studies of PVC by Citrobacter koseri (C. koseri) isolated from the gut of the superworm, Zophobas atratus (Z. atratus) larvae. We also studied the biodegradability of PVC by the gut microbiota compared with C. koseri. We analyzed the microbial degradation of the PVC surface using field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) and confirmed that the physical and chemical changes were caused by C. koseri and the gut microbiota. The chemical structural changes were further investigated using X-ray photoelectron spectroscopy (XPS) and Fourier-transform-infrared (FTIR) spectroscopy, and it was confirmed that the oxidation of the PVC surface proceeded with the formation of carbonyl groups (C = O), and hydroxyl groups (-OH) by C. koseri. Additionally, the gut microbiota composed of diverse microbial species showed equal oxidation of PVC compared to C. koseri. Further, we evaluated the capabilities of single bacterial isolate and gut microbiota for pure PVC film biodegradation. Our results verified that C. koseri and the culturable microbiota from the gut of superworms present similar potential to utilize pure PVC film as a carbon source. These findings provide a potential solution for the biodegradation of unplasticized PVC.

Physicochemical and Structural Evidence that Bacillus cereus Isolated from the Gut of Waxworms (Galleria mellonella Larvae) Biodegrades Polypropylene Efficiently In Vitro.

Biodegradation of plastic waste using microorganisms has been proposed as one of the solutions to the increasing worldwide plastic waste. Polypropylene (PP) is the second most used plastic used in various industries, and it has been widely used in the production of personal protective equipment such as masks due to the COVID-19 pandemic. Therefore, biodegradation of PP becomes very important. Here, we present results on the physicochemical and structural studies of PP biodegradation by Bacillus cereus isolated from the gut of the waxworms, Galleria mellonella larvae. We also studied the biodegradability of PP by the gut microbiota compared with Bacillus cereus. We analyzed the microbial degradation of the PP surface using scanning electron microscopy and energy - dispersive X-ray spectroscopy and confirmed that the physical and chemical changes were caused by Bacillus cereus and the gut microbiota. The chemical structural changes were further investigated using X-ray photoelectron microscopy and Fourier - transform - infrared spectroscopy, and it was confirmed that the oxidation of the PP surface proceeded with the formation of carbonyl groups (C=O), ester groups (C-O), and hydroxyl groups (-OH) by Bacillus cereus. Additionally, the gut microbiota composed of diverse microbial species showed equal oxidation of PP compared to Bacillus cereus. More importantly, high temperature gel permeation chromatography (HT-GPC) analysis showed that Bacillus cereus exhibited quantitatively a higher biodegradability of PP compared to the gut microbiota. Our results suggest that Bacillus cereus possesses a complete set of enzymes required to initiate the oxidation of the carbon chain of PP and will be used to discover new enzymes and genes that are involved in degrading PP. Supplementary Information: The online version contains supplementary material available at 10.1007/s10924-023-02878-y.

Evaluation of the Biodegradation Efficiency of Four Various Types of Plastics by Pseudomonas aeruginosa Isolated from the Gut Extract of Superworms.

Plastic waste worldwide is becoming a serious pollution problem for the planet. Various physical and chemical methods have been tested in attempts to remove plastic dumps. However, these have usually resulted in secondary pollution issues. Recently, the biodegradation of plastic by fungal and bacterial strains has been spotlighted as a promising solution to remove plastic wastes without generating secondary pollution. We have previously reported that a Pseudomonas aeruginosa strain isolated from the gut of a superworm is capable of biodegrading polystyrene (PS) and polyphenylene sulfide (PPS). Herein, we demonstrate the extraordinary biodegradative power of P. aeruginosa in efficiently depolymerizing four different types of plastics: PS, PPS, polyethylene (PE) and polypropylene (PP). We further compared biodegradation rates for these four plastic types and found that PE was biodegraded fastest, whereas the biodegradation of PP was the slowest. Moreover, the growth rates of P. aeruginosa were not always proportional to biodegradation rates, suggesting that the rate of bacterial growth could be influenced by the composition and properties of intermediate molecules produced during plastic biodegradation, and these may supply useful cellular precursors and energy. In conclusion, an initial screening system to select the most suitable bacterial strain to biodegrade certain types of plastic is particularly important and may be necessary to solve plastic waste problems both presently and in the future.

Biodegradation of Polystyrene by Pseudomonas sp. Isolated from the Gut of Superworms (Larvae of Zophobas atratus).

Recently, various attempts have been made to solve plastic waste problems, such as development of biodegradation without producing pollution. Polystyrene (PS) is the fifth most used plastic in many industries; therefore, degrading PS becomes a critical global issue. Here, we reported Pseudomonas aeruginosa strain DSM 50071, initially isolated from the gut of the superworms, Zophobas atratus, and the PS degradation by Pseudomonas sp. DSM 50071. We examined PS degradation using electronic microscopy and measured changes in atomic composition and contact angles with water droplets on the PS surface that represents a chemical change from hydrophobicity to hydrophilicity. We have further examined chemical structural changes using X-ray photoelectron spectroscopy, Fourier-transform-infrared spectroscopy, and nuclear magnetic resonance (NMR) to confirm the formation of carbonyl groups (C═O) in the oxidation pathway during PS biodegradation. In reverse transcription quantitative polymerase chain reaction analysis, the gene expression level of serine hydrolase (SH) in Pseudomonas sp. DSM 50071 was highly increased during PS degradation, and the enzyme-mediated biodegradation of PS was further confirmed by the SH inhibitor treatment test. Thus, the significance of these findings goes beyond the discovery of a novel function of Pseudomonas sp. DSM 50071 in the gut of superworms, highlighting a potential solution for PS biodegradation.

Rapid biodegradation of polyphenylene sulfide plastic beads by Pseudomonas sp.

Pseudomonas sp. isolated from soil, are bioremediating microorganisms that are capable of degrading various types of plastics. Polyphenylene sulfide (PPS) has the most excellent structural stability among general plastics and thus is extremely difficult to break down using physical or chemical methods. This study demonstrates the efficient biodegradation of PPS by Pseudomonas sp., which exists in the gut of superworms. Compared with the conventional film-type of plastic, the degradation efficiencies to the bead form of plastic were significantly improved and thus the biodegradation time was dramatically shortened. Therefore, instead of film-type plastics, we used 300 µm diameter plastic beads for the measurement of Pseudomonas sp.-mediated biodegradation of PPS during a 10-day period. This method not only can be used for comparison and verification of the biodegradation efficiency of different types of plastics within a short reaction time of 10 days, but also provides the possibility to develop a new and more efficient screening system to rapidly identify the most efficient species of bacteria for the biodegradation of various types of plastics.

Publisher Correction: MAOA variants differ in oscillatory EEG & ECG activities in response to aggression-inducing stimuli.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

MAOA variants differ in oscillatory EEG & ECG activities in response to aggression-inducing stimuli.

Among the genetic variations in the monoamine oxidase A (MAOA) gene, upstream variable number tandem repeats (uVNTRs) of the promoter have been associated with individual differences in human physiology and aggressive behaviour. However, the evidence for a molecular or neural link between MAOA uVNTRs and aggression remains ambiguous. Additionally, the use of inconsistent promoter constructs in previous studies has added to the confusion. Therefore, it is necessary to demonstrate the genetic function of MAOA uVNTR and its effects on multiple aspects of aggression. Here, we identified three MAOA alleles in Koreans: the predominant 3.5R and 4.5R alleles, as well as the rare 2.5R allele. There was a minor difference in transcriptional efficiency between the 3.5R and 4.5R alleles, with the greatest value for the 2.5R allele, in contrast to existing research. Psychological indices of aggression did not differ among MAOA genotypes. However, our electroencephalogram and electrocardiogram results obtained under aggression-related stimulation revealed oscillatory changes as novel phenotypes that vary with the MAOA genotype. In particular, we observed prominent changes in frontal γ power and heart rate in 4.5R carriers of men. Our findings provide genetic insights into MAOA function and offer a neurobiological basis for various socio-emotional mechanisms in healthy individuals.

A novel supportive assessment for comprehensive aggression using EEG and ECG.

Aggression is a complex, ubiquitous phenomenon that impacts behavioral traits and psychological health. Assessing aggression is challenging because aggression constitutes multiple subtraits, such as anger, reactive aggression, and overt aggression. Conventional methods of assessing aggression are susceptible to bias because they mainly rely upon self-reports. Thus, more objective methods that provide a multifaceted understanding of aggression in individuals are required. Here, we propose a supportive method of assessing specific aggression subtraits in Koreans using electroencephalography (EEG) and electrocardiography (ECG). Our evaluations and statistical analyses revealed that EEG and ECG signals in subjects responding to video cues that induced aggression are associated with aggression subtraits. In particular, we identified spectral differences in EEG signals in response to stimuli with situation-dependent aggression. The α and ß signals of the Fp2 site (the right ventromedial prefrontal region) are highly associated with anger, reactive aggression, and overt aggression. Moreover, ECG signals are associated with anger and overt aggression. These results link neurobiological findings to psychological explanations of aggression and multiple aspects of human behavior. Our findings can potentially be applied to supportive assessment methods for psychological counseling or psychiatric diagnoses.

Gender Differences in Aggression-related Responses on EEG and ECG.

Gender differences in aggression viewed from an evolutionary and sociocultural perspective have traditionally explained why men engage in more direct and physical aggression, and women engage in more indirect and relational aggression. However, psychological and behavioral studies offer inconsistent support for this theory due to personal or social factors, and little is known about the gender-based neurobiological mechanisms of aggression. This study investigates gender differences in aggression through an analysis of electroencephalography (EEG) and electrocardiography (ECG) based neurobiological responses to commonly encountered stimuli, as well as psychological approaches in healthy Korean youth. Our results from self-reports indicate that overall aggression indices, including physical and reactive/overt aggression, were stronger in men. This agrees with the results of previous studies. Furthermore, our study reveals prominent gender-related patterns in γ signals from the right ventrolateral frontal cortex and changes in heart rate through stimulation by aggressive videos. In particular, gender differences in EEG and ECG responses were observed in response to different scenes, as simple aversion and situation-dependent aggression, respectively. In addition, we discovered decisive gender-distinct EEG signals during stimulation of the situation-dependent aggression regions within the right ventromedial prefrontal and ventrolateral frontal regions. Our findings provide evidence of a psychological propensity for aggression and neurobiological mechanisms of oscillation underlying gender differences in aggression. Further studies of oscillatory responses to aggression and provocation will expand the objective understanding of the different emotional worlds between men and women.

Sod2 overexpression preserves myoblast mitochondrial mass and function, but not muscle mass with aging.

Mice lacking superoxide dismutase-2 (SOD2 or MnSOD) die during embryonic or early neonatal development, with diffuse superoxide-induced mitochondrial damage. Although stem and progenitor cells are exquisitely sensitive to oxidant stress, they have not been well studied in MnSOD2-manipulated mouse models. Patterns of proliferation and differentiation of cultured myoblasts (muscle progenitor cells), PI3-Akt signaling during differentiation, and the maintenance of mitochondrial mass with aging using myoblasts from young (3-4 week old) and aged (27-29 months old) MnSOD2-overexpressing (Sod2-Tg) and heterozygote (Sod2(+/-)) mice were characterized by us. Overexpression of MnSOD2 in myoblasts had a protective effect on mitochondrial DNA abundance and some aspects of mitochondrial function with aging, and preservation of differentiation potential. Sod2 deficiency resulted in defective signaling in the PI3-Akt pathway, specifically impaired phosphorylation of Akt at Ser473 and Thr308 in young myoblasts, and decreased differentiation potential. Compared with young myoblasts, aged myoblast Akt was constitutively phosphorylated, unresponsive to mitogen signaling, and indifferent to MnSOD2 levels. These data suggest that specific sites in the PI3K-Akt pathway are more sensitive to increased superoxide levels than to the increased hydrogen peroxide levels generated in Sod2-transgenic myoblasts. In wild-type myoblasts, aging was associated with significant loss of mitochondrial DNA relative to chromosomal DNA, but MnSOD2 overexpression was associated with maintained myoblast mitochondrial DNA with aging.

Glutathione-peroxidase-1 null muscle progenitor cells are globally defective.

Mice lacking glutathione peroxidase-1 (Gpx1) have decreased resistance to systemically administered oxidants as well as infections, and sustain increased damage after ischemia-reperfusion injuries. However, stem or progenitor cell function in these animals has not been studied. We characterized patterns of proliferation, apoptosis, and differentiation of primary muscle progenitor cells (myoblasts) from Gpx1(-/-) mice. Myoblasts are the transit amplifying compartment of skeletal muscle. All aspects of myoblast biology are negatively affected by deletion of Gpx1. In particular, passaged, proliferating Gpx1(-/-) myoblasts, when induced to differentiate into fused multinucleated myotubes, show significant impairment, and form only a few immature myotubes. This defect occurs despite increased expression of the core regulators of muscle differentiation, the myogenic basic helix-loop-helix (bHLH) transcription factors, in the Gpx1(-/-) myoblasts. Furthermore, Gpx1(-/-) myoblasts exhibited decreased proliferation and increased apoptosis compared to wild-type cells. In vivo, muscle fiber areas are decreased in Gpx1(-/-) vs wild-type mice. These data suggest that Gpx1 is important for adult muscle progenitor cell function at many levels, is necessary for integrity of muscle differentiation, and that quiescent resident stem cell populations may be particularly vulnerable to peroxide-mediated damage.