Gram-positive Anaerobic Bacteria Research Articles

Review on Ethnomedicinal and Potential Effect of Antibacterial Plants against Halitosis

Halitosis is an oral malodor condition in the oral cavity that comes from the breakdown of protein by anaerobic gram-negative and gram-positive bacteria. Some bacteria that are often found in cases of halitosis are Solobacterium moorei, Porphyromonas gingivalis, Tannerella forsythia, Fusobacterium nucleatum, Prevotella intermedia, Treponema denticola, dan Streptococcus mutans. Medicinal plants to treat various diseases have shown minimal side effects. Indonesia is one of the countries that has used plants as traditional medicine since ancient times. As many as 7,000 species of medicinal plants in Indonesia have been studied to address health problems. Among the medicinal plants that have been studied are Green Betel (Piper betle L.), Cinnamon (Cinnamomum zeylanicum), Star Anise (Illicium verum), Mint (Mentha piperita) dan Oregano (Origanum vulgare) which have been shown to cure various diseases. This review article describes the potential of plants as an antibacterial against halitosis. The purpose of this review is to provide an overview of ethnomedicine and the potential effects of antibacterial medicinal plants that can be used in cases of halitosis.

Characterization of a GH Family 43 β-Xylosidase Having a Novel Carbohydrate-binding Module from Paenibacillus xylaniclasticus Strain TW1.

Paenibacillus xylaniclasticus strain TW1, a gram-positive facultative anaerobic bacterium, was isolated as a xylanolytic microorganism from the wastes of a pineapple processing factory. A gene encoding one of its xylanolytic enzymes, a β-xylosidase, was cloned and sequenced. Sequence analysis revealed that this β-xylosidase, named PxXyl43A, was composed of a glycoside hydrolase (GH) family 43 subfamily 12 catalytic module and an unknown function module (UM). The full-length PxXyl43A (PxXyl43A) was heterologously expressed in Escherichia coli and purified. Recombinant PxXyl43A exhibited hydrolysis activity against both p-nitrophenyl-β-D-xylopyranoside (pNPX) and p-nitrophenyl-α-L-arabinofuranoside at specific activities of 250 and 310 mU/mg, respectively. The optimal reaction pH and temperature for pNPX hydrolysis were 7.1 and 54 ˚C, respectively. At pH 7.0 and 54 ˚C, the Km and kcat for pNPX were 1.2 mM and 2.8 ± 0.15 s-1, respectively. It was also discovered that the recombinant unknown function module of PxXyl43A (PxXyl43A-UM) could bind to insoluble xylans like birchwood xylan and oat spelt xylan, whereas it did not bind to cellulosic substrates such as ball-milled cellulose, carboxymethyl cellulose or lichenan. The PxXyl43A-UM's binding constant value Ka for oat spelt xylan was 2.0 × 10-5 M-1. These results suggest that PxXyl43A possesses a novel carbohydrate-binding module, named as CBM91, specific for xylan-containing polysaccharides.

Peptoniphilus coli sp. nov. and Peptoniphilus urinae sp. nov., isolated from humans

Strains Marseille-P3761 and Marseille-P3195 are representatives of two bacterial species isolated from human specimens. Strain Marseille-P3761 was isolated from the stool of a healthy volunteer, while strain Marseille-P3915 was cultivated from the urine of a kidney transplant recipient. Both strains are anaerobic Gram-positive coccoid bacteria. Both are catalase-negative and oxidase-negative and grow optimally at 37 °C in anaerobic conditions. They also metabolize carbohydrates, such as galactose, glucose, fructose, and glycerol. The major fatty acids were hexadecanoic acid for both strains. The highest digital DNA–DNA hybridization (dDDH) values of Marseille-P3761 and Marseille-P3195 strains when compared to their closest phylogenetic relatives were 52.3% and 56.4%, respectively. Strains Marseille-P3761 and Marseille-P3195 shared an OrthoANI value of 83.5% which was the highest value found with Peptoniphilus species studied here. The morphological, biochemical, phenotypic and genomic characteristics strongly support that these strains are new members of the Peptoniphilus genus. Thus, we suggest that Peptoniphilus coli sp. nov., and Peptoniphilus urinae sp. nov., are new species for which strains Marseille-P3761 (CSUR P3761 = CCUG 71,569) and Marseille-P3195 (CSUR P3195 = DSM 103,468) are their type strains, respectively of two new Peptoniphilus species, for which we propose the names Peptoniphilus coli sp. nov. and Peptoniphilus urinae sp. nov., respectively.

Fermentation of soymilk by Lactobacillus acidipiscis isolated from Chinese stinky tofu capable of efficiently biotransforming isoflavone glucosides to dihydrodaidzein and dihydrogenistein.

The soy isoflavone microbial metabolites dihydrodaidzein (DHD), dihydrogenistein (DHG), equol and 5-hydroxy-equol are generally more biologically active than their precursors daidzein and genistein. Bacteria responsible for isoflavone metabolism have been isolated and identified. Fermented soymilk is a potential functional food; however, there are few lactic acid bacteria capable of metabolizing soy isoflavones. A newly isolated Gram-positive facultative anaerobic bacterium, which was named Lactobacillus acidipiscis HAU-FR7, was isolated from the traditional Chinese fermented soy product 'stinky tofu'. Bacterium strain HAU-FR7 can grow under aerobic conditions and can also convert most of the daidzin and genistin in soymilk into DHD and DHG, respectively. The concentrations of DHD and DHG produced were 183 and 134 μmol L-1 , respectively, after fermentation for 24 h. Strain HAU-FR7 does not produce the biogenic amines cadaverine, putrescine, histamine or tyramine, and an antibiotic susceptibility test showed that HAU-FR7 is sensitive to nine of the ten tested antibiotics, except for vancomycin. Moreover, the 1,1-diphenyl-2- picrylhydrazyl free radical scavenging capacity of soymilk fermented with HAU-FR7 was significantly higher than that of unfermented soymilk. A facultative anaerobic lactic acid bacterium, designated Lactobacillus acidipiscis HAU-FR7, is capable of reducing the soy isoflavone glucosides daidzin and genistin in soymilk to DHD and DHG efficiently, even in the presence of atmospheric oxygen. The biotransformation activity of HAU-FR7 grown in soymilk is higher than that in de Man-Rogosa-Sharpe liquid culture medium. © 2022 Society of Chemical Industry.

Gut Microbiota Composition Associated with Clostridioides difficile Colonization and Infection.

Clostridioides difficile is an anaerobic Gram-positive and spore-forming bacterium. The majority of C. difficile strains produce two toxins, A and B, associated with the development of acute diarrhea and/or colitis. In this review, two situations are distinguished: C. difficile infection (CDI) and asymptomatic colonization (AC). The main objective of this review is to explore the available data related to the link between the gut microbiota and the development of CDI. The secondary aim is to provide more information on why some people colonized with toxigenic C. difficile develop an infection while others show no signs of disease. Several factors, such as the use of antibiotics and proton pump inhibitors, hospitalization, and age, predispose individuals to C. difficile colonization and/or C. difficile infection. The gut microbiota of people with AC showed decreased abundances of Prevotella, Alistipes, Bacteroides, Bifidobacterium, Dorea, Coprococcus, and Roseburia. The gut microbiota of people suffering from CDI showed reductions in the abundances of Lachnospiraceae, Ruminococcaceae, Blautia spp., Prevotella spp., Dialister spp., Bifidobacterium spp., Roseburia spp., Anaerostipes spp., Faecalibacterium spp. and Coprococcus spp., in comparison with healthy people. Furthermore, increases in the abundances of Enterococcaceae and Enterococcus were associated with C. difficile infection.

Actinomycosis of the right maxillary sinus mimicking the recurrence of adenoid cystic carcinoma – case presentation

<b>Introduction:</b> Adenoid cystic carcinoma (ACC) is a rare malignancy originating from the salivary glands. It accounts for about 1–5% of all malignancies in the head and neck region. It was first described in 1853 and 1854. The main prognostic factors are tumor extension, degree of malignancy, lymph node metastases, infiltration of neural tissue and the margin of healthy tissues. Actinomycosis is a specific inflammation caused by gram-positive anaerobic bacteria Actinomyces israelii. It was first described by Von Hacker in 1885. These bacteria co-create the bacterial flora of the oral cavity, throat, digestive tract and genitourinary system. Infection with this pathogen triggers formation of abscesses and fistulas. </br></br><b>Case report:</b> A case of a 75-year-old woman treated for ACC is presented. During the follow-up examination, the patient presented symptoms of a local recurrence of ACC, which was suspected until the second histopathological examination that pointed to actinomycosis of the right maxillary sinus. </br></br><b>Conclusion:</b> Due to frequent recurrences of ACC after treatment, follow-up in these patients should be long-term, and any worrying symptoms should be diagnosed for potential recurrence.

Elimination of carbon catabolite repression in Clostridium tyrobutyricum for enhanced butyric acid production from lignocellulosic hydrolysates

Clostridium tyrobutyricum, a gram-positive anaerobic bacterium, is recognized as the promising butyric acid producer. But, the existence of carbon catabolite repression (CCR) is the major drawback for C. tyrobutyricum to efficiently use the lignocellulosic biomass. In this study, the xylose pathway genes were first identified and verified. Then, the potential regulatory mechanisms of CCR in C. tyrobutyricum were proposed and the predicted engineering targets were experimental validated. Inactivation of hprK blocked the CcpA-mediated CCR and resulted in simultaneous conversion of glucose and xylose, although xylose consumption was severe lagging behind. Deletion of xylR further shortened the lag phase of xylose utilization. When hprK and xylR were inactivated together, the CCR in C. tyrobutyricum was completely eliminated. Consequently, ATCC 25755/ΔhprKΔxylR showed significant increase in butyrate productivity (1.8 times faster than the control) and excellent butyric acid fermentation performance using both mixed sugars (11.0–11.9 g/L) and undetoxified lignocellulosic hydrolysates (12.4–13.4 g/L).

Whole-genome sequence analysis of Clostridium chauvoei isolated from clinical case of black quarter (BQ) from India.

Black quarter (BQ) is an infectious disease affecting cattle and small ruminants worldwide caused by Gram-positive anaerobic bacterium Clostridium chauvoei. In this study, a draft genome sequence of C. chauvoei NIVEDIBQ1 strain isolated from clinical case of black quarter was analyzed. Sequence analysis indicated that genome had 2653 predicted coding DNA sequences, harbored numerous genes, mobile genetic elements for pathogenesis, and virulence factors. Computational analysis revealed that strain contained 30 virulence-associated genes. An intact genomic region highly similar to the Clostridium phage was present in the genome. Presence of CRISPR systems and the transposon components likely contribute to the genome plasticity. Strain encode diverse spectrum of degradative carbohydrate-active enzymes (CAZymes). Comparative SNP analysis revealed that the genomes of the C. chauvoei strains analyzed were highly conserved. Phylogenetic analysis of strains and available genome (n = 21) based on whole-genome multi-locus sequence typing (wgMLST) and core orthologous genes showed the clustering of strains into two different clusters suggesting geographical links.

Clostridium difficile Infection (CDI) by Hypervirulent BI/NAP1/027 Strain: a Comprehensive Review of Toxigenicity, Pathogenesis, Risk Factors, and Preventative Measures

Clostridium difficile is an anaerobic bacil gram-positive bacteria, able to form spores and toxin, that is transmitted among humans through the fecal–oral route. Clostridium difficile infection (CDI), a typical nosocomial infection has been contributed to a signifi cant proportion of morbidity and mortality among in-patients with a case-fatality rate of 14% within 30 days after diagnosis. Profound culture and toxin examination for C. difficile are still minimal in many hospitals in various Asian countries. Consequently, C. difficile reports in Asia remain rare. Highly virulent form of C. difficile caused greater fatality and epidemics severity. Elderly age, hospitalization, exposure to antibiotics e.g., cephalosporins, fluoroquinolones, clindamycin, and penicillin contributed as main risk factors. Hypervirulent strain BI/NAP1/027 demonstrated to carry CdtLoc gene locus encodes CD196 ADP-ribosyltransferase (CDT) or known as binary toxin. Virulence factors are TcdA, TcdB, CDTa CDTb in which hypersporulation and mutation of TcD gene by hypervirulent strain led to toxin hyperexpression. Early cases detection, building management team to evaluate patient positive with all C. difficile toxins, hand hygiene improvement, continuation of contact precautions after diarrhea resolution, audit of infection control, and restriction of antimicrobials should be implemented as preventative measures. Focus measures also should emphasize on development of vaccine of C. difficile to boost immune state of elderly people. This review aims to describe severity of disease caused by hypervirulent BI/NAP1/027 C. difficile strain, its mechanism or pathogenesis, risk factors, current treatment options available, along with proposed preventative measures and infection control.

<strong>Antibacterial activity of strawberry fruit extract against <em>Streptococcus sanguinis</em> (ATCC 10556)</strong>

Introduction: Streptococcus sanguinis is a facultative anaerobic Gram-positive bacteria known as a pioneer that plays a role in creating the biofilm in the oral cavity. Strawberry fruit (Fragaria x ananassa) is an edible fruit widely used for the study as their active compound synergy to improve health. This study aims to analyse the antibacterial activity of strawberry fruit against S. sanguinis (ATCC 10556). Methods: An explorative study was conducted with high concentration methanol extract from strawberry fruit. Antibacterial activity was tested on the methanol extract; afterwards, the extract was fractionated and divided into three fractions: water, ethyl acetate, and hexane. Zone of inhibition was used to assess the most effective fraction among those three, then continued by testing for Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). Results: Inhibitory zone of the ethyl acetate fraction from strawberry fruit 1%, 2%, 3% ,4% and 5% sequentially were 7.3 mm,10.2 mm, 12.3 mm, 16.3 mm and 16.1 mm. Ethyl acetate fraction of 4% was the most effective to create the zone of inhibition with a size of 16.3 mm compared to the others. The Minimum Inhibitory Concentration (MIC) value was 0.25%. It was obtained by diluting a 4% ethyl acetate fraction on a microplate. The Minimum Bactericidal Concentration (MBC) was 2%. Conclusion: Ethyl acetate fraction was an effective fraction from strawberry fruit and had antibacterial activity against S. sanguinis with the inhibitory zone in the concentration of 4%, MIC of 0.25%, and MBC of 2%.

Antimicrobial susceptibility testing is crucial when treating Finegoldia magna infections.

Finegoldia magna is an anaerobic gram-positive bacterium that can cause invasive human infections. Recently, a 52-year-old patient suffering from a periprosthetic joint infection (PJI) due to F. magna was treated with cefepime on hemodialysis; however, treatment failed due to relapse caused by antibiotic-resistant strains. Reports on the antimicrobial susceptibility of F. magna clinical isolates are rare. We collected 57 clinical F. magna isolates from Zurich, Switzerland, between September 2019 and July 2020 and tested their antimicrobial susceptibility to investigate the local resistance pattern. Antimicrobial susceptibility testing (AST) was evaluated for nine antibiotics (benzylpenicillin, amoxicillin/clavulanic acid, cefuroxime, cefepime, levofloxacin, rifampicin, metronidazole, doxycycline, and clindamycin) by E-test according to CLSI guidelines. All F. magna strains were susceptible to benzylpenicillin, amoxicillin/clavulanic acid, and metronidazole, while 75% to clindamycin. F. magna isolates showed MIC values lower than species-unrelated breakpoints for cefuroxime, levofloxacin, and cefepime in 93%, 56%, and 32% of the cases, respectively. MIC values for rifampicin and doxycycline were lower than locally determined ECOFFs in 98% and 72% of the cases, respectively. In summary, we recommend the use of benzylpenicillin, amoxicillin/clavulanic acid, or metronidazole without prior AST as first-line treatment option against F. magna PJI infections. If cefuroxime, cefepime, levofloxacin, rifampicin, doxycycline, or clindamycin are used, AST is mandatory.

THE OPTIMIZATION OF THE RESULTS OF CHEMICAL MUSCLE DENERVATION THROUGH THE RECONSTITUTION OF BOTULINUM TOXIN TYPE A IN A STERILE INJECTABLE PHYSIOLOGICAL VEHICLE ENRICHED WITH ZINC

Botulinum toxin type A (TBA) is the most potent neurotoxin from the eight produced serotypes by the anaerobic gram-positive bacteria Clostridium Botulinum. To affect exclusively the nervous tissue, it is classified as neurotoxin. Its action promotes, within the presynaptic ending nerves, by blocking of the release of neurotransmitters, including acetylcholine. This nervous terminal incapacitation by the destruction of the SNAP25 protein binding loops in the SNARE complex is permanent. Labeled as Chemical Muscle Denervation, this non-invasive technique of significant relevance has aroused the interest of professionals and researchers from various areas and promoting a growing offer of new commercial options, protocol variations and clinical trials, in the aesthetic and therapeutic-functional segment. However, it has been observed lately a dissatisfaction of both professionals and patients, regarding the duration of the effects of the toxin, a reason that directly interferes with the interval between sessions, patient comfort and operating cost of treatments. When searching in the basic literature for concepts and justifications for the technical unpleasantness, in an integrated and interrelated way, it was observed that, as in any chemical phenomenon, chemical muscular denervation needs an ideal scenario. The pH level outside the proper standard at the TBA application site or the saline solution itself where the toxin was reconstituted, the sufficiency of zinc molecules for zinc-dependent reactions or even the choice and execution of protocols are simple examples of this need. The new literary focus brought as a diagnosis the existence of technical gaps, named in this study as “GAPs”, and which directly interfere in the success of procedures, when not identified and corrected. Two of these gaps, pH and zinc level will be presented and resolved in this article.

Antibacterial Activity of the Essential Oil From Litsea cubeba Against Cutibacterium acnes and the Investigations of Its Potential Mechanism by Gas Chromatography-Mass Spectrometry Metabolomics.

Cutibacterium acnes (C. acnes) is an anaerobic Gram-positive bacterium generally considered as a human skin commensal, but is also involved in different infections, such as acne and surgical infections. Although there are a variety of treatments, the side effects and the problem of bacterial drug resistance still limit their clinical usage. In this study, we found that essential oil (EO) distilled from fresh mature Litsea cubeba possessed promising antibacterial activity against C. acnes. In order to elucidate its potential mechanism, bacteriostatic activity test, Live/Dead kit assay, scanning electron microscope (SEM), transmission electron microscope (TEM), and metabolomics were employed. In addition, the content of adenosine triphosphate (ATP) in bacterium and the activities of key enzymes involved in critical metabolic pathways were detected using a variety of biochemical assays. The results showed that EO exhibited significant antibacterial activity against C. acnes at a minimum inhibitory concentration (MIC) of 400 μg/mL and a minimum bactericidal concentration (MBC) of 800 μg/mL, and EO could destroy C. acnes morphology and inhibit its growth. Moreover, results from our study showed that EO had a significant effect on the C. acnes normal metabolism. In total, 86 metabolites were altered, and 34 metabolic pathways related to the carbohydrate metabolism, energy metabolism, amino acid metabolism, as well as cell wall and cell membrane synthesis were perturbed after EO administration. The synthesis of ATP in bacterial cells was also severely inhibited, and the activities of key enzymes of the glycolysis and Wood-Werkman cycle were significantly affected (Pyruvate Carboxylase, Malate Dehydrogenase and Pyruvate kinase activities were decreased, and Hexokinase was increased). Taken together, these results illustrated that the bacteriostatic effect of EO against C. acnes by breaking the bacterial cell morphology and perturbing cell metabolism, including inhibition of key enzyme activity and ATP synthesis. The results from our study may shed new light on the discovery of novel drugs with more robust efficacy.

On the Potential Significance of the Intrinsically Disordered Regions in the Clostridiodes difficile Toxins A and B.

Clostridiodes (or Clostridium) difficile is a spore-forming, Gram-positive anaerobic bacterium that may cause symptoms ranging from diarrhea to pseudomembranous colitis. During the C. difficile infection (CDI), the two primary bacterial toxins, toxin A (TcdA) or toxin B (TcdB), disrupt host cell function mainly through the inactivation of small GTPases that regulate the actin cytoskeleton. Both toxins have complex structural organization containing several functional domains. Analytical bioinformatics tools are used to compare the extent of disorder within TcdA and TcdB proteins, and to see if the existence of structural disorder can be used to explain the difference in the functionality of these toxins. This paper's aim is to offer an overall review of the structural and functional differences between TcdA and TcdB. Results of our multifactorial bioinformatics analysis revealed that intrinsic disorder may play a role in the multifunctionality of C. difficile major toxins TcdA and TcdB, suggesting that intrinsic disorder may be related to their pathogenic mechanisms.

Infecciones por enterococos

Enterococci are facultative anaerobic gram-positive bacteria that are arranged in chains or pairs. The most relevant species are Enterococcus faecalis and Enterococcus faecium. They are normal colonizers of the digestive system. They can survive on surfaces and in hospital settings for an extended period of time. Frequent contact with hospitals, comorbidities, prior antibiotic use, and presence of medical devices are associated with a greater risk of infection. They can give rise to multiple clinical syndromes and are more common in healthcare-associated infections than community infections. Of note are urinary tract infections, intra-abdominal infections, venous catheter-related bacteremias, endocarditis, meningitis, and surgical wound infections. The presence of endocarditis must be evaluated in all enterococci bacteremias; the NOVA and DENOVA scores are useful for doing so. Enterococcus faecalis tend to be sensitive to ampicillin, which is the treatment of choice. In cases of endocarditis or complicated bacteremia, it is recommended to combine them with ceftriaxone or gentamicin. Enterococcus faecium tend to be resistant to ampicillin and the treatment of choice is vancomycin. Treatment of vancomycin-resistant enterococci is not well-defined and represents a challenge; the main options are daptomycin at high doses or linezolid. Adequate control of the source of the infection is fundamental in the management of enterococcal infections.

OnabotulinumtoxinA for the treatment of headache: an updated review.

Botulinum toxin (BT) is a neurotoxin produced by Clostridium botulinum, a gram-positive anaerobic bacterium. Systemic human intoxication from BT following oral ingestion results in acute and life-threatening muscle paralysis called botulism. BT has a wide scope of therapeutic uses, including conditions associated with increased muscle tone, smooth muscle hyperactivity, salivation, sweating, and allergies, as well as for cosmetic purposes. Several commercial forms of BT are available for medical use, including Botox (onabotulinumtoxinA). Multiple studies have found evidence of an analgesic effect of onabotulinumtoxinA and demonstrated the benefits of its use for the treatment of various chronic pain disorders. In this review, we provide an update on the use of onabotulinumtoxinA for the treatment of headache disorders.

JCS/JHRS 2021 guideline focused update on non-pharmacotherapy of cardiac arrhythmias.

JCS/JHRS 2021 guideline focused update on non-pharmacotherapy of cardiac arrhythmias.

Actinomycosis in head-and-neck region – A review

Actinomycosis is an uncommon chronic disease caused by filamentous Actinomyces, a Gram-positive anaerobic bacterium that usually colonizes in the human oral cavity, digestive tract, and genital area. Actinomycosis is rarely seen chronic infectious disease in the head-and-neck region. The clinical presentations are often nonspecific and mimic several diseases of the head-and-neck area such as malignancy and tuberculosis. Moreover, investigations such as imaging, fine-needle aspiration, and biopsy are often nonspecific. The diagnosis of actinomycosis is still difficult for the diagnosis at present time. Bacterial culture and histopathological study are the cornerstones of the diagnosis but a particular situation is needed to get the exact diagnosis. The prolonged bacterial cultures in anaerobic conditions are required to confirm the bacterium and classical microscopic findings like necrosis with yellowish sulfur granules and filamentous Gram-positive fungal-like pathogens. The surgical excision of the lesion/mass along with appropriate antibiotic therapy is important treatment options. Clinicians must be aware of the typical clinical presentations of actinomycosis in the head-and-neck region as it may mimic the malignant process in the head-and-neck area. Actinomycosis patients need prolonged high doses of penicillin G or amoxicillin and the period of antimicrobial treatment can be shortened to a minimum of 3 months in patients in whom optimum surgical resection of the infected tissues has been useful.

Terrisporobacter glycolicus Bacteremia in a Patient With Cirrhosis

Terrisporobacter is an anaerobic gram-positive bacterium causing infection in postoperative patients, particularly those with comorbidities, and is rarely linked to the disease process itself. Photoclinic

马尾松幼苗根系和光合碳供应对土壤性质变化和温室气体排放的驱动作用

PDF HTML阅读 XML下载 导出引用 引用提醒 马尾松幼苗根系和光合碳供应对土壤性质变化和温室气体排放的驱动作用 DOI: 10.5846/stxb202008012004 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划(2017YFC0505503)；国家自然科学基金面上项目(31370627) Root input and photosynthetic carbon supply effect on soil properties and greenhouse gases release of Pinus massoniana seedling Author: Affiliation: Fund Project: The National Key Technologies R&D Program of China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:森林植被受全球气候变化、森林经营活动及病虫害等多种干扰,导致林地光合碳供应水平及根系输入量发生变化。在此背景下,土壤性质及土壤温室气体排放的响应及其机理是预测森林碳汇功能变化及森林可持续经营的重要依据。以2年生马尾松盆栽苗为对象,通过单株/盆和3株/盆栽植密度控制根系输入量、通过环割和截干控制光合碳向地下的供应能力,模拟森林植被干扰导致的根系输入量及光合碳供应变化对土壤理化性质、微生物群落结构及温室气体排放的影响。结果表明,苗木根系非结构性碳水化合物(TNC)含量和氮含量比单株/盆低;3株/盆的土壤速效氮含量比单株/盆低,土壤革兰氏阳性菌、厌氧菌、放线菌及丛枝菌根真菌丰富度均比单株/盆显著增加,3株/盆的土壤二氧化碳(CO2)排放速率较高,但土壤氧化亚氮(N2O)排放速率差异不显著。无论是单株/盆还是3株/盆,环割和截干处理后,根系生物量、根系长度及表面积均比对照显著下降;根系TNC含量显著下降。土壤和根系氮含量都有增加趋势;土壤微生物生物量碳(SMBC)含量降低,而土壤微生物生物量氮(SMBN)则提高。环割和截干后,土壤中各种微生物组成丰富度均有下降趋势,土壤CO2排放速率显著下降,土壤N2O排放速率则显著提高。根系输入量及光合碳供应对土壤细菌和真菌含量均有显著影响,土壤细菌含量与根系生物量、SMBC和SMBN显著正相关;土壤真菌含量与土壤温度显著负相关,与根系生物量、SMBC和SMBN显著正相关。相关分析表明,土壤CO2排放通量与土壤温度、土壤湿度及根系生物量显著正相关,与土壤硝态氮显著负相关;土壤N2O排放通量与土壤温度和土壤湿度显著正相关。以上研究表明,根系输入量与地上光合碳供应共同作用,改变土壤理化性质及微生物环境,进而影响土壤温室气体排放。 Abstract:Forest vegetation is affected by climate change, forest management activities, and diseases and pests, which can lead to changes in photosynthetic carbon supply, root input of forest land, composition of soil microbial community, and soil greenhouse gases emission. These changes and their underlying mechanisms are the basis for modelling change of forest ecological functions and for managing forest scientifically. Here, we studied level of root input of 2-year-old potted seedlings of Pinus massoniana under two densities, single-plant/pot and 3-plants/pot, and under two disturbance treatments, ring-barking and stem-severing to stop carbon transport to the root system. We aimed to simulate the effects of changes in root input and photosynthetic carbon supply on soil physical and chemical properties, microbial community structure and greenhouse gas emission under various conditions. Our results showed that the total nonstructural carbohydrate (TNC) and nitrogen in seedling roots were lower in 3-plants/pot treatment than in single-plant/pot treatment. The content of soil available nitrogen in 3-plants/basins was lower than that in single-plant/pot. In contrast, richness of soil Gram-positive bacteria, anaerobic bacteria, actinomycetes and arbuscular mycorrhizal fungi were higher in 3-plants/pot treatment than in single-plant/pot treatment. Further, the emission rate of soil carbon dioxide (CO2) was higher in 3-plants/pot treatment than in single-plant/pot treatment. Planting density had no significant effects on emission rate of soil nitrous oxide (N2O). Both the ring-barking and stem-severing treatments decreased the root biomass, root length, root surface and root TNC content in both single-plant/pot and 3-plants/pot treatments. Both the ring-barking and stem-severing treatments increased the content of nitrogen in soil and roots, the content of soil microbial biomass nitrogen (SMBN), and emission rate of soil N2O, but decreased the content of soil microbial biomass carbon (SMBC), the richness of soil microbial and the emission rate of soil CO2. Root biomass input and photosynthetic carbon supply have significant effect on soil bacterial and fungal contents. Soil bacterial contents were positively correlated with root biomass, SMBC and SMBN. Soil fungal content was negatively correlated with soil temperature, positively correlated with root biomass, SMBC and SMBN. Correlation analysis showed that soil CO2 emission flux was positively correlated with soil temperature, soil humidity and root biomass, while negatively correlated with soil nitrate nitrogen; soil N2O emission flux was positively correlated with soil temperature and soil humidity. The results suggest that root input and photosynthetic carbon supply work together to change soil physical and chemical properties and microbial environment, thus contribute to changes in the emissions rate of soil greenhouse gases. 参考文献 相似文献 引证文献