3种水稻土中7株固氮蓝细菌的分离与特征

【背景】蓝细菌是水生和陆地生态系统中生物固氮的主要贡献者。【目的】增加对稻田土壤固氮蓝细菌的了解,获得用于进一步研究的可培养固氮蓝细菌菌株。【方法】选择3种具有不同固氮能力的水稻土,采用BG11-N培养基分离培养固氮蓝细菌菌株,对新分离菌株进行形态特征观察,通过基因组DNA的nifH基因扩增明确其固氮潜力,进一步采用乙炔还原法和~(15)N_2示踪法定量测定其固氮能力,通过基因组DNA的16SrRNA基因序列比对进行鉴定。【结果】在光照培养条件下,采用BG11-N培养基共分离纯化得到自养菌株7株,细胞呈圆形或椭圆形、单列、无分枝、丝状和念珠状,在固体培养基上形成团垫状菌落。新分离菌株在BG11-N培养基中生长状况良好,以基因组DNA为模板可扩增出nifH基因,乙炔还原法和~(15)N_2示踪法测定结果显示具有较高固氮能力,同时具有铁载体生成能力。结合16S rRNA基因序列比对和形态特征,7株菌被初步鉴定隶属于念珠藻科(Nostocaceae)。【结论】从水稻土中分离到在稻田生物固氮中发挥重要作用的蓝细菌(念珠藻科)菌株,可培养固氮蓝细菌菌株固氮能力较高,兼具铁载体生成能力,可作为进一步深入研究的微生物资源,具有潜在的研究应用价值。     

嗜热蓝细菌碳酸酐酶基因的异源表达及酶学性质

【背景】碳酸酐酶(carbonic anhydrase,CAH)因其高效催化CO2转化为HCO3–的能力成为当今碳减排工艺中的研究热点,但因工厂烟道气的温度较高,因此寻求热稳定性高的嗜热碳酸酐酶是碳酸酐酶仿生学固碳的关键所在。【目的】克隆嗜热蓝细菌Thermosynechococcuselongatus PKUAC-SCTE542和SynechococcuslividusPCC6715的碳酸酐酶基因Ecah、Pcah,实现其在大肠杆菌细胞中异源高效表达,并进行初步酶学性质研究。【方法】利用PCR技术获得碳酸酐酶基因cah,构建重组基因工程菌BL21_pETM11_CAH,利用IPTG诱导方法高效表达蛋白,表达产物(CAH)经Ni-Agarose亲和层析柱纯化后,进行酶学性质研究。【结果】从E542、PCC6715中克隆得到大小均为534 bp的碳酸酐酶基因,以CO2为底物,酶催化CO2水合的活性分别为42.6 WAU/mg-protein、47.6 WAU/mg-protein。碳酸酐酶ECAH 50°C处理30 min后,酶活提高了8%,而PCAH却下降了10%。Zn2+、磺胺对两种碳酸酐酶有显著抑制作用,Ca2+对ECAH有轻微激活作用,对PCAH无显著抑制作用。【结论】E542嗜热蓝细菌表达的碳酸酐酶比PCC6715的热稳定性强,符合处理工业高温点源烟道气的CO2的基本要求,丰富了碳减排的嗜热碳酸酐酶基因库。     

乳酸菌对微囊藻毒素的清除

【目的】研究唾液乳杆菌(Lactobacillus salivarius BBE09-18)、发酵乳杆菌(L.fermentum BBE09-29)以及干酪乳杆菌(L.casei Zhang)对藻毒素的清除能力以及影响乳酸菌清除藻毒素的主要因素,以期为进一步解析乳酸菌清除藻毒素的作用机制提供理论基础,并为去除食品体系中的藻毒素提供新的思路。【方法】研究乳酸菌细胞的不同生理状态(活细胞与死细胞)对藻毒素清除能力的影响,考察菌浓差异、起始藻毒素浓度差异、葡萄糖的供给等对乳酸菌清除藻毒素效能的影响。【结果】3株实验乳酸菌均具有清除藻毒素的能力,其中,L.casei Zhang的藻毒素清除能力最强,当藻毒素初始浓度为150μg/L时,24h后残留藻毒素浓度为85.5μg/L,清除率可达43%。此外,研究还发现乳酸菌活细胞的清除能力显著高于热失活后的死细胞。添加外源物质葡萄糖能显著提高实验菌株清除藻毒素的效率,在初始浓度为1800μg/L的藻毒素溶液中,当添加5%(w/v)葡萄糖后,L.casei Zhang经24h可清除92%的藻毒素。【结论】3株乳酸菌均具有藻毒素清除能力;同时,菌体浓度以及菌体自身的生理状态对藻毒素的清除效率具有重要影响,乳酸菌对藻毒素的清除可能与菌体的代谢活性相关。     

滨海盐渍化土壤中蓝细菌多样性及分布

【目的】蓝细菌在贫瘠土壤的固氮、固碳中发挥着重要作用,然而土壤盐渍化对蓝细菌多样性及群落结构的影响还不清楚。本研究以莱州湾南岸及黄河口海水入侵盐渍化土壤为例,研究蓝细菌的多样性、群落结构及丰度沿盐度梯度的分布情况。【方法】利用自动核糖体间隔基因分析(ARISA)技术与群落相似性分析(ANOSIM)探究蓝细菌群落的差异与空间分布格局;通过16S rRNA基因克隆文库、测序与系统进化分析解析了3个典型盐度梯度样品中蓝细菌的群落组成;实时定量PCR测定蓝细菌16S rRNA拷贝数(丰度);BEST多元分析探寻影响蓝细菌分布的主要环境因子。【结果】蓝细菌在莱州湾南岸盐土中分布广泛,其群落结构在低(0.63%?1.27%)、中(1.55%?2.00%)、高盐度(2.39%?5.11%)样品组之间差异显著(P=0.03),而在不同含水量样品组间则不显著(P=0.09)。总体来看,群落结构主要受土壤盐度与含水量这两个因子联合控制(P=0.02)。低盐样品中蓝细菌多样性和丰富度最低,并以Halomicronema和Acaryochloris为优势类群。Leptolyngbya在中、高盐土中占优势。Arthrospira与Geitlerinema仅在低盐土中检测到,而Oscillatoria则仅出现在高盐土中。随盐度升高蓝细菌丰度呈下降趋势,低盐土样中蓝细菌丰度(2.14×105 copies/g干土)显著高于中盐土(1.25×105 copies/g干土)(P<0.05);高盐度土为1.20×105 copies/g干土。【结论】盐渍化程度是调控莱州湾南岸滨海土壤中蓝细菌群落结构与丰度的最重要环境因子,可能对滨海土壤微生物碳氮循环产生重要影响。     

溶藻细菌BS01产二异丁氧基苯基对塔玛亚历山大藻生长的影响

摘要:【目的】利用一株溶藻细菌BS01分泌的杀藻化合物(二异丁氧基苯基)胺作用于赤潮藻———塔玛亚历山大藻(Alexandrium tamarense),研究该化合物对塔玛亚历山大藻的作用效果及可能的作用机制。【方法】利用10和20μg/mL的杀藻化合物处理塔玛亚历山大藻,观察藻细胞的响应。【结果】研究发现,利用20μg/mL的杀藻化合物处理藻,24 h后杀藻率达到84.1%,此时细胞内叶绿素a的含量仅为对照的58.5%。而当对藻细胞最大光化学效率(Fv/Fm)进行测定时发现,20 μg/mL的浓度处理24 h后,最大光化学效率相比于对照细胞降低了55.5%,这说明藻细胞的光合作用过程受到抑制。细胞内部的活性氧(ROS)水平在处理0.5 h后即开始增高,并导致细胞内部的脂质过氧化,使细胞内丙二醛(MDA)的含量上升。藻细胞的抗氧化酶如超氧化物歧化酶(SOD)和过氧化氢酶(CAT)的活性也有不同程度的增高,以清除细胞内部的活性氧。利用透射电镜观察发现,20 μg/mL的浓度处理24 h后,细胞内重要的细胞结构解体,细胞严重空泡化,显示出细胞死亡的特征。【结论】杀藻化合物(二异丁氧基苯基)胺能够通过引起藻细胞内部氧化损伤的方式引起藻细胞的死亡,同时该化合物仅针对少数几种藻类具有杀藻效果,因此该杀藻化合物在赤潮的治理方面具有较好的应用前景。     

天山乌鲁木齐河源一号冰川表面粉尘蓝细菌群落结构及其系统发育

【目的】揭示天山乌鲁木齐河源一号冰川表面粉尘中蓝细菌多样性、群落结构及其系统发育,为科学评价冰川表面及相关环境中功能微生物的地球化学循环作用提供参考依据。【方法】采用两对蓝细菌16S rRNA基因特异引物扩增并构建克隆文库,基于序列相似性归类OTU并统计多样性,代表OTU序列与NCBI、RDP数据库比对后构建系统发育树。【结果】天山一号冰川表面粉尘101个蓝细菌克隆序列基于97%的相似性被划分为12个OTU,shannon多样性指数为1.522,系统发育分析显示主要隶属于颤蓝细菌目(Oscillatoriales)和色球蓝细菌目(Chroococcales)。Oscillatoriales包括席蓝细菌属(Phormidium)、微鞘蓝细菌属(Microcoleus)、伪鱼腥蓝细菌属(Pseudanabaena)和颤蓝细菌属(Oscillatoria)4个属,其中Phormidium占绝对优势,68个克隆序列划分为4个OTU,其它3个属的序列较少。Chroococcales仅有1个克隆,与亚球形管胞蓝细菌(Chamaesiphon subglobosus)亲缘关系很近。此外,发现一号冰川表面粉尘的速效磷、速效钾含量是冰川退缩前沿50 m-500 m距离土壤的2-5倍,硝态氮达到10-20倍,有机质含量达到3-9倍,显著高于冰川前沿环境。【结论】天山一号冰川表面粉尘蓝细菌的多样性指数相对较高,以隶属于Phormidium属的成员占绝对优势,对其生态学作用需进一步深入探究。     

集胞藻PCC6803高效基因表达平台的构建与评价

针对蓝细菌代谢工程改造的需求,成功构建了可以在模式蓝细菌菌株集胞藻PCC6803中高效表达外源基因的3个基因组整合表达平台,以及1个可以在多株蓝细菌中表达的广宿主穿梭表达平台。该表达平台通过选用集胞藻PCC6803中1,5-二磷酸核酮糖缩化酶/氧化酶的启动子驱动外源基因的表达,应用“SD-AUG”翻译融合的策略提高外源蛋白翻译效率,以及加入终止子序列Trbc以提高转录终止效率,实现了对外源基因的高效表达。利用lacZ作为报告基因,检测了所构建表达平台pFQ20在集胞藻中的基因表达效率,结果显示β-半乳糖苷酶的活性为109 Miller。同时,基于pFQ20表达平台在集胞藻PCC6803中表达了来自大肠杆菌的硫酯酶基因tesA’,蛋白印迹实验结果显示了硫酯酶的成功表达。该表达平台为在蓝细菌中开展遗传研究及基因工程改造提供了有用的遗传工具,其构建策略为在蓝细菌中构建高效稳定的外源基因表达元件提供了借鉴。     

实验室适应性进化技术在光合蓝细菌底盘工程中的研究进展

蓝细菌是唯一可进行放氧光合作用的原核微生物,基于光合蓝细菌构建“自养型细胞工厂”具有广阔前景。但以蓝细菌作为底盘进行生物燃料及化学品的合成仍存在细胞耐受能力差、产量低等问题,导致实现工业化生产的经济可行性还比较低,亟需通过合成生物学等技术手段构建新的藻株。近年来,实验室适应性进化(adaptive laboratory evolution,ALE)已被用于底盘工程中,实现了优化生长速度、增加耐受性、加强底物利用和提高产品产量等目标。ALE在提高蓝细菌鲁棒性方面取得了一定进展,已获得了耐受高光、重金属离子、高盐和高浓度有机溶剂胁迫的进化藻株。但是,蓝细菌中的ALE策略效率相对较低,耐受各胁迫的分子机制并未阐释完全。本文综述了ALE相关技术策略及其在蓝细菌底盘工程中的应用,讨论了如何借鉴其他微生物中ALE手段,构建更大ALE突变文库、增加菌株的突变频率、缩短进化时间、探索多重胁迫耐受工程菌构建原则及研究策略等,高效解析进化菌株的突变体库,构建高产量、鲁棒性强的工程菌株等,以期未来促进蓝细菌底盘的改造及其工程菌的规模化应用。     

粟酒裂殖酵母核糖体蛋白RPL21表达不足引发细胞粘附

【目的】随机选择裂殖酵母核糖体蛋白RPL21作为研究对象,分析其表达不足对细胞的影响。【方法】通过同源臂交换的方法,敲除裂殖酵母基因组中RPL21蛋白的编码基因rpl21-1和rpl21-2,观察突变菌株rpl21-1Δ和rpl21-2Δ细胞内的核糖体合成情况以及细胞表型变化。【结果】突变菌株rpl21-1Δ和rpl21-2Δ细胞内总的rpl21(rpl21-1+rpl21-2)表达水平与野生型菌株相比分别减少了66.5%和58.7%,合成的核糖体总量较野生型菌株分别下降了62.8%和50.4%。突变菌株在YEPD液体培养基中培养时发生细胞粘附现象,而基因回补的重组菌株rpl21-1Δ/RPL21-1和rpl21-2Δ/RPL21-2突变株细胞中粘附现象消失。【结论】核糖体蛋白损伤造成核糖体合成受阻,进而引发细胞生长过程中的粘附在粟酒裂殖酵母中是普遍存在的现象。     

微宇宙模拟溢油条件下沉积物中蓝细菌多样性

【目的】在不同浓度原油胁迫下,研究沉积物中原油降解规律及蓝细菌的响应机制,探讨蓝细菌对原油的耐受程度,并揭示蓝细菌种属结构组成的演替规律,为预测和判断溢油污染是否会造成富营养化等次生环境问题提供依据。【方法】建立微宇宙模拟实验体系,设置未添加原油对照组(CK组)及一系列高浓度原油处理组(25、125和250 g/kg干重,分别为LO组、MO组和HO组),通过气相色谱-氢火焰离子化检测器分析微宇宙培养期间原油降解规律。采用蓝细菌16SrRNA基因分析蓝细菌多样性和丰度变化规律,以及蓝细菌各种属的演替情况。【结果】微宇宙培养第31天时,在最低浓度处理组(LO组)沉积物表层出现片状绿色菌苔,而其他处理组和对照组未出现此现象。蓝细菌16SrRNA基因克隆文库结果表明,在溢油条件下所有处理组的蓝细菌多样性均降低,但有一些种属出现富集,如Oscillatoria和Prochlorococcus等。此外,也监测到大量的不可培养种属,预示着沉积物中可能存在新种属的蓝细菌。【结论】蓝细菌对原油具有较高耐受性,25 g/kg浓度原油会对蓝细菌生长产生刺激作用,且可能进一步引起蓝细菌富集。原油会引起蓝细菌多样性降低,但个别种属会发生富集,说明这些种属对原油具有较高耐受性,甚至发挥重要功能,如Oscillatoria具有固氮功能。本研究在分子水平上研究了蓝细菌对原油的响应,对蓝细菌分子生态研究具有重要意义。     

骆驼瘤胃耐受/降解去氢骆驼蓬碱细菌的筛选

【目的】中药骆驼蓬含多种生物碱,对动物有毒性。生活于荒漠半荒漠的骆驼可采食部分有毒植物而不中毒。为了解骆驼瘤胃微生物对骆驼蓬植物毒素的耐受与降解能力进行本研究。【方法】以含100mg/L纯品去氢骆驼蓬碱的M98-5培养基接种骆驼瘤胃内容物,经五代胁迫培养后分离可耐受/降解去氢骆驼蓬碱的细菌,以薄层析法检验其降解活力,以16SrRNA序列分析其进化地位。【结果】29个分离株中15株具有降解去氢骆驼蓬碱活性;16SrRNA序列分析显示,属于乳杆菌属(Lactobacillus)16株,占55%;志贺氏菌属(Shigella)7株,占24%;芽孢杆菌属(Bacillus)4株,占13.8%;肠球菌属(Enterococcus)和巨型肠球菌属(Megasphaera)各1株。【结论】可耐受/降解去氢骆驼蓬碱的骆驼瘤胃细菌仅限于少数几类,且检测到的具有降解活力的只有乳杆菌类。     

The photoregulated expression of multiple phycocyanin species. A general mechanism for the control of phycocyanin synthesis in chromatically adapting cyanobacteria

The regulation of phycocyanin synthesis in response to growth in chromatic illumination was studied in 69 strains of cyanobacteria. Cyanobacteria (24 of 31 strains examined), which chromatically adapt by modulating the synthesis of both phycocyanin and phycoerythrin, controlled phycocyanin synthesis through the differential, photoregulated expression of two phycocyanin species (two alpha-type and two beta-type subunits). For these strains the expression of one pair of phycocyanin subunits was constitutive (i.e. irrespective of the light wavelength in which the cells were grown); the expression of the second pair of phycocyanin subunits occurred specifically during growth in red light. Two facultatively heterotrophic cyanobacteria, Calothrix strains 7101 and 7601, synthesized both the constitutive and the inducible pairs of phycocyanin subunits when grown heterotrophically in the dark after transfer from either red or green light. No evidence for the existence of multiple and/or photoregulated phycocyanin species was found for cyanobacteria (25 strains) incapable of chromatic adaptation, nor for cyanobacteria (13 strains) which chromatically adapt by modulating the synthesis of phycoerythrin alone.     

Molecular characterization of marine Cyanobacteria from the Indian subcontinent deduced from sequence analysis of the phycocyanin operon (cpcb-IGS-cpcA) and 16S-23S ITS region

Molecular characterization of ten marine cyanobacterial isolates belonging to the order Oscillatoriales was carried out using the phycocyanin locus (cpcBA-IGS) and the 16S-23S internally transcribed spacer region. DNA sequences from the phycocyanin operon discriminated ten genotypes, which corresponded to seven morphotypes identified by traditional microscopic analysis. The cpcB coding region revealed 17 % nucleotide variation, while cpcA exhibited 29 % variation across the studied species. Phylogenetic analyses support the conclusion that the Phormidium and Leptolyngbya genera are not monophyletic. The nucleotide variations were heterogeneously distributed with no or minimal informative nucleotides. Our results suggest that the discriminatory power of the phycocyanin region varies across the cyanobacterial species and strains. The DNA sequence analysis of the 16S-23S internally transcribed spacer region also supports the polyphyletic nature of the studied oscillatorian cyanobacteria. This study demonstrated that morphologically very similar strains might differ genotypically. Thus, molecular approaches comprising different gene regions in combination with morphological criteria may provide better taxonomical resolution of the order Oscillatoriales.     

Isolation and characterization of a mesophilic Arthrospira maxima strain capable of producing docosahexaenoic acid

A strain of the cyanobacterium Arthrospira was isolated from Lake Chahannaoer in northern China and was characterized according to microscopic morphology, photosynthetic oxygen-evolving activity, growth rate, and nutritional profile. Compared with thermophilic Arthrospira species occurring naturally in tropical and subtropical lakes, this isolate is mesophilic and grows optimally at ~20 degreesC. The total protein, fatty acid, phycocyanin, carotenoid, and chlorophyll a contents were 67.6, 6.1, 4.32, 0.29, and 0.76 grams per 100 grams of dry weight, respectively. The strain is rich in polyunsaturated fatty acids (PUFAs). An essential omega-3 fatty acid, docosahexaenoic acid (DHA), was detected, and gamma-linolenic acid (GLA) and DHA accounted for 28.3% of the total fatty acid content. These features of this newly isolated strain make it potentially useful in commercial mass culture in local areas or as a biofuel feedstock. It is also an alternative resource for studying the metabolic PUFA pathways and mechanisms of cold stress tolerance in cyanobacteria.     

Identification of thermophilic and marine bacilli from shallow thermal vents by restriction analysis of their amplified 16S rDNA

AIMS: In order to identify 73 thermophilic isolates from shallow, marine thermal vents of Eolian Islands, we compared their restriction patterns of amplified 16S rDNA with those of nine well described Bacillus species and eight Eolian Bacillus strains. METHODS AND RESULTS: This study allowed to assign 57 (78%) isolates to different Bacillus species. Nineteen field strains were recognised as representatives of four described species, namely B. thermodenitrificans, "B. caldolyticus", B. vulcani and B. stearothermophilus. The profiles of 38 isolates matched instead, those of seven Eolian strains (B. thermodenitrificans strain A2, B. licheniformis strain B3-15, and five novel species, represented by Bacillus strain 1bw, Bacillus strain 4-1, Bacillus strain 5-2, Bacillus strain 10-1, Bacillus strain 1as). Among the 16 unidentified isolates, seven restriction patterns were recognised. CONCLUSIONS: This study showed that restriction analysis of amplified 16S rDNA is useful for a rapid and reliable identification of strains belonging to described species as well as for recognition of new species. SIGNIFICANCE AND IMPACT OF THE STUDY: This work revealed a high taxonomic diversity among the thermophilic bacilli isolated from Eolian Islands and a distinct distribution of the species within the Eolian hydrothermal vent system.     

Analysis of common epitopes on gag proteins of HIV-1, HIV-2 and SIV[AGM] using monoclonal antibodies against HIV-1.

Five monoclonal antibodies (MoAbs) to gag proteins of HIV-1 were prepared in mice. Western blot analyses showed that three clones recognized p24 and the other two p17. Among the three MoAbs recognizing p24, all recognized two of three strains of HIV-2. The spectra of reactions to SIV[AGM] of these MoAbs against p24 were different from one to another; K3-24 recognized all four strains of SIV[AGM], L6-24 three of them, and K5-24 none of them. Of the two MoAbs recognizing p17, K7-17 recognized two of the three strains of HIV-2 but not any SIV[AGM] strain, and the other clone, L14-17 recognized none of analogous proteins of HIV-2 nor of SIV[AGM]. These results demonstrate that the gag proteins of HIV-2 and SIV[AGM] share some common epitopes with those of HIV-1 which are heterogenic in some degree among the different isolates.     

Halomonas aidingensis sp. nov., a moderately halophilic bacterium isolated from Aiding salt lake in Xinjiang, China

Two Gram-negative moderately halophilic bacterial strains, designated Ad-1(T) and C-12, were isolated from Aiding salt lake of Xinjiang in China. The novel isolates were subjected to a polyphasic taxonomic study. Cells of these strains were cocci or short rods and motile with polar flagella. Colonies produced brown-red pigment. The isolates grew in the range of 0.5-25% (w/v) NaCl, pH 5.5-10.5 and 4-45°C. Analysis of their 16S rRNA gene sequences indicated that strains Ad-1(T) and C-12 belonged to the genus Halomonas showing 92.7-98.4% similarity with the type species. The isoprenoid quinones of the isolates were Q-9 and Q-8. The major cellular fatty acids were C18:1ω7c, C16:1ω7c/6c, C16:0, C12:0-3OH and C10:0. The DNA G + C contents of strains Ad-1(T) and C-12 were 64.6 and 63.9 mol%, respectively. The DNA relatedness between the two isolates was 89.2%. The similarities of these newly isolated strains with closely related type strains were lower than 35% at the genetic level. Based on phenotypic, chemotaxonomic and genetic characteristics, the representative strain Ad-1(T) is considered to be a novel species of the genus Halomonas, for which the name Halomonas aidingensis sp. nov. is proposed, with Ad-1(T) (= CGMCC 1.10191(T) = NBRC 106173(T)) as the type strain.     

Fimbriation, hemagglutination and adherence properties of fresh clinical isolates of Branhamella catarrhalis.

This study investigated the fimbriation on 24 fresh clinical isolates of Branhamella catarrhalis by electron microscopy. All the strains were isolated from patients with respiratory infections. The Branhamella catarrhalis strains were classified into three groups according to the grade of fimbriation. Among these 24 strains the incidence of densely fimbriated, moderately fimbriated and sparsely fimbriated isolates were 12 (50%), 7 (29%) and 5 (21%), respectively. After five-times serial subculture on Brain Heart Infusion agar, the average number of fimbriae per bacteria was decreased from 174 to 114 in the densely fimbriated strain and from 48 to 10 in the moderately fimbriated strain. Moreover, 20% of the population became non-fimbriated in moderately fimbriated strain after the serial subculture. In strains with higher hemagglutination titer the number of fimbriae was significantly (P < 0.04) more than in strains with lower hemagglutination titer.     

Polyphasic characterization of benthic, moderately halophilic, moderately thermophilic cyanobacteria with very thin trichomes and the proposal of Halomicronema excentricum gen. nov., sp. nov.

A new genus of moderately halophilic, moderately halotolerant and moderately thermophilic cyanobacteria with very thin trichomes is described. The four strains included in this genus were isolated from benthic microbial mats in a man-made hypersaline pond. Trichomes were around 1 microm thick, with small constrictions at the cross-walls and diffluent colorless sheaths. Thylakoids were parallel to the cell wall, but thylakoids and nucleoid were often excentrically arranged within the cytoplasm with respect to the main trichome axis. Strains grew at between 3.2 and 12-15% (w/v) salinity with optima between 3.2 and 12%. They showed lower temperature limits around 20 degrees C and upper limits between 45 and 50 degrees C, with optima between 28 and 45-50 degrees C. Carotenoid and mycosporine amino-acid complements were identical among strains. Phylogenetic analyses based on 16S rRNA gene sequence showed that all strains were closely related (99% or higher similarity) and distantly related to other cyanobacteria (91% or lower similarity). We propose the new genus and species Halomicronema excentricum for these strains. The type strain is TFEP1.     

Isolation and characterization of two novel ethanol-tolerant facultative-anaerobic thermophilic bacteria strains from waste compost

In a search for potential ethanologens, waste compost was screened for ethanol-tolerant thermophilic microorganisms. Two thermophilic bacterial strains, M5EXG and M10EXG, with tolerance of 5 and 10% (v/v) ethanol, respectively, were isolated. Both isolates are facultative anaerobic, non-spore forming, non-motile, catalase-positive, oxidase-negative, Gram-negative rods that are capable of utilizing a range of carbon sources including arabinose, galactose, mannose, glucose and xylose and produce low amounts of ethanol, acetate and lactate. Growth of both isolates was observed in fully defined minimal media within the temperature range 50–80°C and pH 6.0–8.0. Phylogenetic analysis of the 16S rDNA sequences revealed that both isolates clustered with members of subgroup 5 of the genus Bacillus. G+C contents and DNA–DNA relatedness of M5EXG and M10EXG revealed that they are strains belonging to Geobacillus thermoglucosidasius. However, physiological and biochemical differences were evident when isolates M5EXG and M10EXG were compared with G. thermoglucosidasius type strain (DSM 2542^T). The new thermophilic, ethanol-tolerant strains of G. thermoglucosidasius may be candidates for ethanol production at elevated temperatures.