Isolation and investigation of anaerobic microorganisms involved in methanol transformation in an underground gas storage facility

High methanol and acetate concentrations (up to 12 and 14 g l⁻¹, respectively) were found in water samples collected at different objects of the North Stavropol underground gas storage facility (UGSF), and significant seasonal variations in the content of these compounds were revealed. The dominant anaerobic microorganisms isolated from these samples during the study belonged to acetogens, methanogens, and sulfate reducers. The results of 16S rRNA gene sequencing and analysis of the physiological properties showed that the isolates were close to the species of Eubacterium limosum, Sporomusa sphaeroides, Methanosarcina barkeri, Methanobacterium formicicum, and Desulfovibrio desulfuricans. The isolated organisms, except for Methanobacterium formicicum, were capable of methylotrophic growth. All strains were characterized by resistance to high methanol concentrations (up to 40–50 g l⁻¹). Their other energy substrate was hydrogen. The combination of the growth characteristics of these strains (pH, temperature, and salinity ranges) was shown to correspond to the ecological situation observed in the UGSF. The results of investigation of the isolated strains suggest that organic acids (acetate, butyrate) found in high concentrations in the initial samples are metabolic products of the revealed acetogens. Based on the established biological peculiarities of the isolated strains of methanogens, acetogens, and sulfate-reducing bacteria, these microorganisms may be considered as the main agents of anaerobic transformation of methanol and some other organic and inorganic compounds in UGSFs.     

Cultivated anaerobic acidophilic/acidotolerant thermophiles from terrestrial and deep-sea hydrothermal habitats

Metabolic and phylogenetic diversity of cultivated anaerobic microorganisms from acidic continental hot springs and deep-sea hydrothermal vents was studied by molecular and microbiological methods. Anaerobic organotrophic enrichment cultures growing at pH 3.5–4.0 and 60 or 85°C with organic energy sources were obtained from samples of acidic hot springs of Kamchatka Peninsula (Pauzhetka, Moutnovski Volcano, Uzon Caldera) and Kunashir Island (South Kurils) as well as from the samples of chimneys of East Pacific Rise (13°N). The analyses of clone libraries obtained from terrestrial enrichment cultures growing at 60°C revealed the presence of archaea of genus Thermoplasma and bacteria of genus Thermoanaerobacter. Bacterial isolates from these enrichments were shown to belong to genera Thermoanaerobacter and Thermoanaerobacterium, being acidotolerant with the pH optimum for growth at 5.5–6.0 and the pH minimum at 3.0. At 85°C, domination of thermoacidophilic archaea of genus Acidilobus in terrestrial enrichments was found by both molecular and microbiological methods. Five isolates belonging to this genus possessed some phenotypic features that were new for this genus, such as flagellation or the ability to grow on monosaccharides or disaccharides. Analyses of clone libraries from the deep-sea thermoacidophilic enrichment cultures showed that the representatives of the genus Thermococcus were present at both 60 and 85°C. From the 60°C deep-sea enrichment, a strain belonging to Thermoanaerobacter siderophilus was isolated. It grew optimally at pH 6.0 with the minimum pH for growth at 3.0 and with salinity optimum at 0–2.5% NaCl and the maximum at 7%, thus differing significantly from the type strain. These data show that fermentative degradation of organic matter may occur at low pH and wide temperature range in both terrestrial and deep-sea habitats and can be performed by acidophilic or acidotolerant thermophilic prokaryotes.     

Atrazine degradation by aerobic microorganisms isolated from the rhizosphere of sweet flag (Acorus calamus L.)

In presented study the capability of microorganisms isolated from the rhizosphere of sweet flag (Acorus calamus) to the atrazine degradation was assessed. Following isolation of the microorganisms counts of psychrophilic bacteria, mesophilic bacteria and fungi were determined. Isolated microorganisms were screened in terms of their ability to decompose a triazine herbicide, atrazine. Our results demonstrate that within the rhizosphere of sweet flag there were 3.8 × 10⁷ cfu of psychrophilic bacteria, 1.8 × 10⁷ cfu of mesophilic bacteria, and 6 × 10⁵ cfu of fungi per 1 g of dry root mass. These microorganisms were represented by more than 20 different strains, and at the first step these strains were grown for 5 days in the presence of atrazine at a concentration of 5 mg/l. In terms of the effect of this trial culture, the bacteria reduced the level of atrazine by an average of about 2–20%, but the average level of reduction by fungi was in the range 18–60%. The most active strains involved in atrazine reduction were then selected and identified. These strains were classified as Stenotrophomonas maltophilia, Bacillus licheniformis, Bacillus megaterium, Rahnella aquatilis (three strains), Umbelopsis isabellina, Volutella ciliata and Botrytis cinerea. Culturing of the microorganisms for a longer time resulted in high atrazine degradation level. The highest degradation level was observed at atrazine concentrations of 5 mg/l for S. maltophilia (83.5% after 15 days of culture) and for Botrytis sp. (82% after 21 days of culture). Our results indicate that microorganisms of the sweet flag rhizosphere can play an important role in the bioremediation of atrazine-contaminated sites.     

Characterization of technetium(vII) reduction by cell suspensions of thermophilic bacteria and archaea

Washed cell suspensions of the anaerobic hyperthermophilic archaea Thermococcus pacificus and Thermoproteus uzoniensis and the anaerobic thermophilic gram-positive bacteria Thermoterrabacterium ferrireducens and Tepidibacter thalassicus reduced technetium [⁹⁹Tc(VII)], supplied as soluble pertechnetate with molecular hydrogen as an electron donor, forming highly insoluble Tc(IV)-containing grayish-black precipitate. Apart from molecular hydrogen, T. ferrireducens reduced Tc(VII) with lactate, glycerol, and yeast extract as electron donors, and T. thalassicus reduced it with peptone. Scanning electron microscopy and X-ray microanalysis of cell suspensions of T. ferrireducens showed the presence of Tc-containing particles attached to the surfaces of non-lysed cells. This is the first report on the reduction in Tc(VII) by thermophilic microorganisms of the domain Bacteria and by archaea of the phylum Euryarchaeota.     

Screening of bacterial strains capable of converting biodiesel‐derived raw glycerol into 1,3‐propanediol, 2,3‐butanediol and ethanol

The ability of bacterial strains to assimilate glycerol derived from biodiesel facilities to produce metabolic compounds of importance for the food, textile and chemical industry, such as 1,3‐propanediol (PD), 2,3‐butanediol (BD) and ethanol (EtOH), was assessed. The screening of 84 bacterial strains was performed using glycerol as carbon source. After initial trials, 12 strains were identified capable of consuming raw glycerol under anaerobic conditions, whereas 5 strains consumed glycerol under aerobiosis. A plethora of metabolic compounds was synthesized; in anaerobic batch‐bioreactor cultures PD in quantities up to 11.3 g/L was produced by Clostridium butyricum NRRL B‐23495, while the respective value was 10.1 g/L for a newly isolated Citrobacter freundii. Adaptation of Cl. butyricum at higher initial glycerol concentration resulted in a PD_max concentration of ～32 g/L. BD was produced by a new Enterobacter aerogenes isolate in shake‐flask experiments, under fully aerobic conditions, with a maximum concentration of ～22 g/L which was achieved at an initial glycerol quantity of 55 g/L. A new Klebsiella oxytoca isolate converted waste glycerol into mixtures of PD, BD and EtOH at various ratios. Finally, another new C. freundii isolate converted waste glycerol into EtOH in anaerobic batch‐bioreactor cultures with constant pH, achieving a final EtOH concentration of 14.5 g/L, a conversion yield of 0.45 g/g and a volumetric productivity of ～0.7 g/L/h. As a conclusion, the current study confirmed the utilization of biodiesel‐derived raw glycerol as an appropriate substrate for the production of PD, BD and EtOH by several newly isolated bacterial strains under different experimental conditions.     

北疆传统发酵生奶酪中乳酸菌的耐受性及益生特性测定

【背景】北疆乳制品中生奶酪作为发酵乳制品,其中有多种微生物的参与,是优质食品级微生物的宝贵来源,然而其中蕴含的丰富的微生物资源也面临着流失。【目的】研究已筛选出的41株乳酸菌的生长曲线变化规律,并对其在低pH环境的耐酸特性及益生特性进行分析。【方法】通过人工模拟胃肠液和含0.3%、0.5%、1.0%浓度牛胆盐溶液培养,对从生奶酪中分离鉴定的41株乳酸菌菌株进行人工胃肠液、牛胆盐耐受性试验。【结果】41株乳酸菌中有6株乳酸菌(编号为QM-5、QM-27、UM-12、UM-18、NM-11和NM-14)均能在pH值分别为2.0、2.5、3.0、3.5、4.0时生长较好,在pH 2.0的环境下也保持一定程度的生长。菌株存活率大于50%,乳酸菌含量为108 CFU/mL以上。从生奶酪分离的乳酸菌有极强的耐酸、耐胆盐特性,可以预测在胃肠道环境生存。41株菌对大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)和枯草芽孢杆菌(Bacillus subtilis)均有抑制作用。【结论】通过比较耐酸性、胃肠道模拟、胆盐耐受性和抑菌特性等实验结果,初...     

An Integrated System for the Bioremediation of Wastewater Containing Xenobiotics and Toxcic Metals

An integrated system for the biotreatment of acidic wastewaters containing both toxic metals and organics is presented. It consists of two bioprocess stages (i) an anaerobic, SRB stage (containing alkaline‐tolerant s ulfate‐ r educing b acteria) that at pH 8 (chosen to acclimatize the bacteria in the biomedium) produces high concentrations of total sulfide ions (more than 400 mg/L) which are added to the wastewater to precipitate the heavy metals out at pH 2 as metal sulfides, and (ii) an aerobic, acidophilic stage containing heterotrophic bacteria (WJB3) that degrade organic xenobiotics. The anaerobic system was comprised of a 4‐L fluidized bed bioreactor with immobilized SRB, a mixing tank, and a precipitation tank. The effluent from the bioreactor with a high concentration of sulfide ions was fed into a mixing tank where model wastewaters containing toxic metals and phenol at pH 2 were also fed at increasing loading rates until free metal ions could be detected in the precipitation tank outlet. Then the effluent from the precipitation tank outlet was fed into a 2.5‐L aerobic bioreactor in which phenol was degraded. In this research, 100 % removal efficiencies were obtained with wastewaters containing more than 400 mg/L metal ions and 900 mg/L phenol at a 6‐h HRT of the mixing tank.     

Acido-thermophilic Bacteria from Thermal Waters

Three strains of acido-thermophilic bacteria were isolated from hot-spring waters of Tohoku district in Japan. They were aerobic spore-forming bacilli and identified to belong to genus Bacillus. Their characteristics were as follows. They were acidophilic, and grew well in the pH range of between 2.3 and 5.0. Optimal growth conditions were 65°C for temperature and 3.5~4.0 for pH of media. Strains T-4 and T-17 required biotin as growth factor, but T-7 did not require any factors for its growth. These bacteria were different from Bacillus stearothermophilus or B. coagulans in their taxonomic properties.     

Characteristics of the bacteriocin produced by <Emphasis Type="Italic">Lactococcus lactis</Emphasis> subsp. <Emphasis Type="Italic">cremoris</Emphasis> CTC 204 and the effect of this compound on the mesophilic bacteria associated with raw beef

Summary >Screening for the bacteriocin production of strains of lactic acid bacteria from various meat and meat products resulted in the detection of a bacteriocin-producing Lactococcus lactis subsp. cremoris CTC 204, isolated from chicken. The bacteriocin inhibited not only closely related lactic acid bacteria (Lactobacillus helveticus), but also pathogenic microorganisms (Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and Clostridium perfringens). It was inactivated by α-chymotrypsin, ficin, papain, and pronase E, but not by lipase or pepsin. This compound was heat stable even at autoclaving temperature (121°C for 10min) and was produced during refrigerated storage. It was also active over a wide pH range (2–10), but the highest activity was observed in the lower pH range. The results indicated that dipping raw beef in the bacteriocin produced by strain CTC 204 could contribute to the extension of the shelf life of refrigerated bovine meat.     

Isolation and characterization of microorganisms able to produce 1,3-propanediol under aerobic conditions

Microbial fermentation under strictly anaerobic conditions has been conventionally used for the production of 1,3-propanediol, a key raw material required for the synthesis of polytrimethylene terephthalate (PTT) and other polyester fibers. In the current study, we have identified eight strains of microorganism which are able to produce 1,3-propanediol under aerobic condition. Those strains were isolated from garden soil, which were enriched by culturing in LB medium with glycerol added under aerobic condition. The identities of those strains were established based on their 16S rRNA sequences and physiological characteristics. Results indicated 6 strains are Citrobacter freundii and 2 strains are Klebsiella pneumoniae subsp Penumoniae. One of Klebsiella pneumoniae subsp Penumoniae strains, designated as TUAC01, demonstrated comparable levels of 1,3-propanediol oxidoreductase, glycerol dehydratase and glycerol dehydrogenase activity to the anaerobic microorganisms described in the literature. Accordingly, in larger scales (5 l) fed-batch culture the TUAC01 strain showed a remarkable 1,3-propanediol producing potency under aerobic conditions. 60.1 g/l of 1,3-propanediol was yield after 42 h incubation in an agitating bioreactor; and in air-lift bioreactor 66.3 g/l of 1,3-propanediol was yield after 58.5 h incubation. The aerobic ferment process, reduced the product cost and made the biological method of 1,3-propanediol production more attractive.     

Polyamine patterns in iron- and sulphur-oxidizing bacteria isolated from an Indian copper mine indicate requirement of spermidine for growth under acid conditions

Spermidine was found to be the predominant polyamine in all the acidophilic as well as neutrophilic strains of chemolithotrophic iron- and sulphur-oxidizing bacteria and associated organotrophic cultures inhabiting a copper mining ecosystem. Adaptation of neutrophilic Thiobacillus thioparus strain to pH 5.0 was found to increase the spermidine content of the cells 2.3 times while the biomass yield decreased by 50%. However, exogenous supplementation of spermidine could restore the biomass yield to levels obtainable at pH 7.0. These observations indicate that spermidine plays a significant role in adaptive behaviour of microorganisms in natural ecosystems, especially under acid conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Formation of N-Carboxymethyl Amino Acid from the Reaction of α-Amino Acid with Glyoxal

Enrichment cultures in a medium containing 0.1% methanol and 0.1% bicarbonate at pH 7.0 under anaerobic conditions in the light became mainly green in color. Forty-four enrichment cultures, which showed abundant growth, were obtained from 46 different sources and found to contain cells of methanol-utilizing bacteria and green algae as predominant members. From these enrichment cultures, two strains of bacteria and two strains of algae were isolated. The microorganisms isolated were designated as bacterium No. 7, bacterium No. 8, Chlorella sp. A-1 and Chlorella sp. B-1, respectively. Stable mixed cultures were easily formed by mixing the isolated cultures of bacteria and algae. Both methanol and bicarbonate were necessary for the growth of the mixed cultures under anaerobic-light conditions. Growth behavior of the mixed cultures was examined on a medium containing 0.1% methanol and 0.1 % bicarbonate at 30°C in the light (about 6000 lx). The maximum specific growth rate for the cultures, µ_max, was 0.092 hr^?1 (doubling time, 7.5 hr). The maximum cell yield was 0.87 g dry-cell weight per g of methanol used. The protein content of the biomass was 65%.     

花生根际微生物的分离及高效功能菌株筛选

【背景】花生根际分布着丰富的微生物类群，分离筛选多种功能的高效微生物是研发高效复合菌肥的基础。【目的】从花生根际土壤及根表分离微生物，分析可培养微生物的多样性，筛选高效解有机磷和无机磷、产吲哚乙酸(indole-3-acetic acid, IAA)和铁载体功能的菌株，为研发花生微生物菌肥打下基础。【方法】利用稀释涂布法，从采自山东省栖霞市、平度市、烟台市莱山区 3个样点的花生根际土、根表样品中分离微生物，基于16S rRNA基因序列对其进行系统发育分析，并通过初筛和复筛筛选高效解磷、产IAA和铁载体的菌株。【结果】共分离、纯化、保藏147株菌，其中75株分离自根际土壤，72株分离自根表样品。系统发育分析表明所有的菌分布于放线菌门(Actinomycetota)、芽孢杆菌门(Bacillota)、拟杆菌门(Bacteroidota)和假单胞菌门(Pseudomonadota)这4个门的40个属，优势属为链霉菌属(Streptomyces, 21.77%)、芽孢杆菌属(Bacillus, 16.33%)；根表样品微生物的多样性高于根际样品；共筛选到解有机磷菌株62株，短波单胞菌(Brevundimonas) YTU21021解有机磷能力最强为1.12 mg/L；解无机磷菌株31株，不动杆菌(Acinetobacter) YTU21009解无机磷能力最强为7.04 mg/L；产IAA的菌株63株，肠杆菌(Enterobacter) YTU21054产IAA量最高，达184.19 mg/L；产铁载体细菌7株，伯克氏菌(Burkholderia) YTU21051产铁载体能力最强，A_s/A_r为0.90。【结论】花生根际和根表样品中可培养微生物多样性较为丰富，本研究筛选到的高效功能菌丰富了花生根际功能微生物资源，为后续与高效根瘤菌联合研发花生复合微生物菌肥奠定了基础。     

Microbial transformation of chlorinated benzoates

Chlorinated benzoates enter the environment through their use as herbicides or as metabolites of other halogenated compounds. Ample evidence is available indicating biodegradation of chlorinated benzoates to CO₂ and chloride in the environment under aerobic as well as anaerobic conditions. Under aerobic conditions, lower chlorinated benzoates can serve as sole electron and carbon sources supporting growth of a large list of taxonomically diverse bacterial strains. These bacteria utilize a variety of pathways ranging from those involving an initial degradative attack by dioxygenases to those initiated by hydrolytic dehalogenases. In addition to monochlorinated benzoates, several bacterial strains have been isolated that can grow on dichloro-, and trichloro- isomers of chlorobenzoates. Some aerobic bacteria are capable of cometabolizing chlorinated benzoates with simple primary substrates such as benzoate. Under anaerobic conditions, chlorinated benzoates are subject to reductive dechlorination when suitable electron-donating substrates are available. Several halorespiring bacteria are known which can use chlorobenzoates as electron acceptors to support growth. For example, Desulfomonile tiedjei catalyzes the reductive dechlorination of 3-chlorobenzoate to benzoate. The benzoate skeleton is mineralized by other microorganisms in the anaerobic environment. Various dichloro- and trichlorobenzoates are also known to be dechlorinated in anaerobic sediments.     

Molecular Identification of Acidophilic Manganese (Mn)-Solubilizing Bacteria from Mining Effluents and Their Application in Mineral Beneficiation

The study of the microbial ecology in extreme acidic environments has provided an important foundation for the development of mineral biotechnology. The present investigation reports the isolation, identification and molecular characterization of indigenous manganese (Mn) solubilizing acidophilic bacterial strains from mine water samples from Odisha, India. Four morphologically distinct bacterial strains showing visible growth on Mn-supplemented plates of varying pH were isolated and identified. Mn solubilizing ability of the isolates was tested by growing them on Mn-supplemented agar plates. The appearance of lightening around the growing colonies of all the isolates demonstrated their Mn solubilizing ability in the medium. 16 S rRNA sequencing was carried out and the bacterial isolates were taxonomically classified as Enterobacter sp. AMSB1, Bacillus cereus AMSB3, Bacillus nealsonii AMSB4 and Staphylococcus hominis AMSB5. The evolutionary timeline was studied by constructing neighbor-joining phylogenetic trees. The ability of acidophilic microorganisms to solubilize heavy metals is supported by five basic mechanisms which include: enzymatic conversion, metal effluxing, reduction in sensitivity of cellular targets, intra- or extracellular sequestration, and permeability barrier exclusion. Such ecological studies undoubtedly will provide insights into Mn biogeochemical processes occurring in leaching environments. The application of acidophilic microbiology in mineral biorecovery and beneficiation has a large future potential.     

Effects of glycerol on the growth,adhesion, and cellulolytic activity of rumen cellulolytic bacteria and anaerobic fungi

The effect of glycerol on the growth, adhesion, and cellulolytic activity of two rumen cellulolytic bacterial species,Ruminococcus flavefaciens andFibrobacter succinogenes subsp.succinogenes, and of an anaerobic fungal species,Neocallimastix frontalis, was studied. At low concentrations (0.1–1%), glycerol had no effect on the growth, adhesion, and cellulolytic activity of the two bacterial species. However, at a concentration of 5%, it greatly inhibited their growth and cellulolytic activity. Glycerol did not affect the adhesion of bacteria to cellulose. The growth and cellulolytic activity ofN. frontalis were inhibited by glycerol, increasingly so at higher concentrations. At a concentration of 5%, glycerol totally inhibited the cellulolytic activity of the fungus. Thus, glycerol can be added to animal feed at low concentrations.     

烟草根际可培养微生物多样性及防病促生菌的筛选

[背景] 根际微生物在植物根部生态系统中扮演着重要角色,影响着植物的营养吸收和健康生长。[目的] 了解常年不发病烟田烤烟品种K326根际可培养微生物的多样性,筛选具有防病促生功能的菌株,为烟草病害绿色防控提供资源。[方法] 采用传统培养方法对烟草根际土壤中的细菌和真菌进行分离鉴定,评价菌株的促生特性及病原菌拮抗能力,并进一步验证典型菌株对盆栽烟苗的促生效果。[结果] 共获得261株微生物菌株,包括160株细菌和101株真菌。经分子鉴定,细菌中以变形菌门（Proteobacteria）和厚壁菌门（Firmicutes）为主要类群;真菌中以子囊菌门（Ascomycota）和毛霉菌门（Mucoromycota）为主要类群。在属水平上,细菌以假单胞菌属（Pseudomonas）和芽孢杆菌属（Bacillus）为主,真菌以曲霉属（Aspergillus）和青霉属（Penicillium）为主。从不同种水平上进一步选择44株细菌为代表菌株,发现它们均具有不同程度的吲哚-3-乙酸（Indole-3-Acetic Acid,IAA）产生能力,9株能够溶解有机磷,16株能够溶解无机磷,13株产生铁载体,14株产生生1-氨基环丙烷-1-羧酸（1-Aminocyclopropane-1-Carboxylate,ACC）脱氨酶。从160株细菌中筛选得到抑制青枯病菌和黑胫病菌的菌株数目分别为25、26株。经盆栽试验发现韩国假单胞菌（P. koreensis） HCH2-3、浅黄绿假单胞菌（P. lurida） FGD5-2和贝莱斯芽孢杆菌（B. velezensis） EM-1对烟苗呈现不同程度的促生作用,其中3株菌联合施加对烟苗的促生效果最明显。[结论] 烟草根际存在着丰富多样的具有防病促生潜力的微生物,并且合成菌群或功能互补的菌株联合施用是未来微生物菌剂研发的重要方向。     

Isolation and characterization of xylose- and xylan-utilizing anaerobic bacteria

By enrichment with xylose, nine mesophilic strains of anaerobic bacteria were obtained from various sources. Two isolates appear to belong to the genus Eubacterium. Six other strains belong to the genus Clostridium. Three of the isolated strains utilized larch wood xylan. The percentage of utilization of xylose and xylan and the yield of fermentation end products — viz. acetic acid and butyric acid-are equivalent to that of Clostridium acetobutylicum (ATCC 824) and reported thermophilic strains.     

Co-cultivation of Thermoanaerobacter strains with a methanogenic partner enhances glycerol conversion

Glycerol-rich waste streams produced by the biodiesel, bioethanol and oleochemical industries can be treated and valorized by anaerobic microbial communities to produce methane. As current knowledge of the microorganisms involved in thermophilic glycerol conversion to methane is scarce, thermophilic glycerol-degrading methanogenic communities were enriched. A co-culture of Thermoanaerobacter and Methanothermobacter species was obtained, pointing to a non-obligately syntrophic glycerol degradation. This hypothesis was further studied by incubating Thermoanaerobacter brockii subsp. finnii and T. wiegelii with glycerol (10 mM) in pure culture and with different hydrogenotrophic methanogens. The presence of the methanogen accelerated glycerol fermentation by the two Thermoanaerobacter strains up to 3.3 mM day⁻¹, corresponding to 12 times higher volumetric glycerol depletion rates in the methanogenic co-cultures than in the pure bacterial cultures. The catabolic pathways of glycerol conversion were identified by genome analysis of the two Thermoanaerobacter strains. NADH and reduced ferredoxin formed in the pathway are linked to proton reduction, which becomes thermodynamically favourable when the hydrogen partial pressure is kept low by the hydrogenotrophic methanogenic partner.     

Invasive bark beetle‐associated microbes degrade a host defensive monoterpene

Conifers respond to herbivore attack with defensive chemicals, which are toxic to both insects and their associated microorganisms. Microorganisms associated with insects have been widely reported to metabolize toxic chemicals, which may help both microorganisms and host insects overcome host conifer defense. Dendroctonus valens LeConte, an introduced exotic pest from North America to China, has killed millions of healthy pines. Alpha‐pinene is the most abundant defensive monoterpene in Chinese Pinus tabuliformis. Although microorganisms associated with D. valens have already been investigated, little is known about their bioactivities when encountering host defensive monoterpenes. In this study, we evaluated the influences of different concentrations of α‐pinene to D. valens and the three most frequently isolated yeasts and bacteria of D. valens, and further assayed microorganisms’ capabilities to degrade α‐pinene. Results showed that the gallery lengths and body weight changes of bark beetles were significantly affected by 6 mg/mL and 12 mg/mL of α‐pinene applied in media compared to controls. The tolerance of experimental microorganisms to α‐pinene varied depending on the microbial species. Two out of three yeast strains and all three bacterial strains degraded 20%–50% of α‐pinene compared to controls in 24 h in vitro. The microorganisms capable of α‐pinene degradation in vitro and their tolerance to high levels of α‐pinene suggested that D. valens‐associated microorganisms may help both microorganisms and the bark beetle overcome host α‐pinene defense.