宏基因组技术及其在环境保护和污染修复中的应用

宏基因组学是分子生物学技术应用于微生物生态学研究而形成的一个新概念,以环境中末培养微生物为研究对象,通过直接从环境样品中提取全部微生物的DNA,构建宏基因组文库,利用基因组学策略研究环境样品所包含的全部微生物的遗传组成及其群落功能.从1998年提出至今,该项技术已经广泛应用于工业、农业、医学等研究领域.文章在对宏基因组学的概念、研究方法、存在问题的综述基础上提出了相应的解决方法,并指出该技术在环境保护和污染修复中存在潜在的应用价值.利用该技术可以深入了解特定环境中微生物空间分布和动态变化,为环境监测、预警和评价提供理论依据.     

酸雨致酸土壤对小麦幼苗若干营养代谢的影响

通过模拟酸雨淋洗土壤,造成土壤酸化和盐基流失.将小麦幼苗栽培于由酸雨致酸的土壤,其体内的碳素代谢和氮素代谢受到抑制,从而导致体内可溶性糖含量和含N量下降.其中致酸土壤对根系碳素代谢和氮素代谢的抑制作用大于对茎叶碳素代谢和氮素代谢的抑制作用.表4参23     

盐碱湖硫循环及嗜盐嗜碱硫功能菌研究进展

硫循环是地球化学元素循环之一,微生物在其中发挥关键的驱动作用.深入认识微生物驱动的硫循环过程,将有助于探究生物地球化学循环机制.盐碱湖因具有完整的硫循环途径、丰富的硫功能菌种类,已成为研究硫地球化学循环的理想环境.总结近年来有关盐碱湖硫元素循环过程及嗜盐嗜碱性硫功能菌的研究进展.包括基于多种组学的盐碱湖微生物多样性分析以及嗜盐嗜碱性硫功能菌的应用,重点分析已经分离或完成测序的嗜盐嗜碱性硫氧化菌(11个属24个种)和硫还原菌(15个属25个种)的生理生化特点及系统发育关系,并且总结硫代谢基因的分布规律,明确盐碱湖中微生物硫代谢主要途径,其中细胞色素C硫化氢脱氢酶和Sox氧化酶系组成盐碱湖中硫氧化的最主要途径.初步形成了盐碱湖硫循环过程概貌、较完整的嗜盐嗜碱硫功能菌谱系及硫代谢途径,这将对认识地球硫元素循环,尤其是盐碱湖硫循环具有重要意义.建议将来加强开展有关异养硫氧化菌代谢过程、硫碳氮代谢之间关系及相互作用、影响硫循环过程的关键环境因子及调控手段等研究,进一步推进嗜盐嗜碱性硫功能菌的应用.(图7表4参83)     

功能宏基因组学在新型抗生素耐药基因研究中的应用进展

抗生素耐药性是二十一世纪人类面对的最严峻的环境健康问题之一.抗生素耐药基因(Antibiotics resistance genes, ARGs)被认为是一类新型环境污染物.当前针对ARGs的主要研究方法有细菌分离和培养法、聚合酶链式反应(Polymerase Chain Reaction,PCR)法、和宏基因组法.然而,仅有功能宏基因组方法能发现新型的ARGs.功能宏基因组方法利用新一代测序技术的高通量的特性,结合分子生物学技术和功能筛选构建有关抗生素耐药性的基因库,通过生物信息学分析高效地发现新型ARGs.本文综述了近来利用功能宏基因组技术筛选新型ARGs的相关研究进展,总结了功能宏基因学相关的技术和方法的优势和限制,并展望了功能宏基因学方法进一步发展的方向.     

环境微生物中芳环加氧酶的获取策略

芳环加氧酶可催化芳香环的羟基化反应,广泛应用于生物修复及化工合成行业.本文在综述芳环加氧酶的分类和应用的基础上,详细探讨基于纯培养技术与宏基因组技术的芳环加氧酶开发策略,并首次对这些策略进行比较和评估.利用传统的纯培养技术已经获得大量的芳环加氧酶,然而这些加氧酶种类单一,重复率高,且新颖性不足.新兴的宏基因组技术赋予了开发未培养微生物资源的新思路,但利用其获取芳环加氧酶的研究刚刚起步,存在着筛选效率低、异源表达困难等难题.本文从基因信息量、筛选通量与效率、时间与成本以及目的基因下游表达可行性等方面对这两种方法进行综合评价,并提出宏基因组技术筛选不同类型芳环加氧酶的适用方法.纯培养技术与宏基因组技术的有机结合,与蓬勃发展的各种组学技术一起,将有助于推动芳环加氧酶的理论研究及生物催化产业的快速发展.     

产甲烷生化代谢途径研究进展

微生物产甲烷过程产生的甲烷约占全球甲烷产量的74%.产甲烷过程对生物燃气生产和全球气候变暖等都有着重要的意义.本文综述了产甲烷菌的具体生化代谢途径,其本质是产甲烷菌利用细胞内一系列特殊的酶和辅酶将CO2或甲基化合物中的甲基通过一系列的生物化学反应还原成甲烷.在这一过程中,产甲烷菌细胞能够形成钠离子或质子跨膜梯度,驱动细胞膜上的ATP合成酶将ADP转化成ATP以获得能量.根据底物类型的不同,可以将该过程分为3类:还原CO2途径、乙酸途径和甲基营养途径.还原CO2途径是以H2或甲酸作为主要的电子供体还原CO2产生甲烷,其中涉及到一个最新的发现——电子歧化途径;乙酸途径是乙酸被裂解产生甲基基团和羧基基团,随后,羧基基团被氧化产生电子供体H2用于还原甲基基团;甲基营养途径是以简单甲基化合物作为底物,以外界提供的H2或氧化甲基化合物自身产生的还原当量作为电子供体还原甲基化合物中的甲基基团.通过这3种途径产甲烷的过程中,每消耗1mol底物所产生AT P的顺序为还原CO2途径>甲基营养途径>乙酸途径.由于产甲烷菌自身难以分离培养,未来将主要通过现代的生物技术和计算机技术,包括基因工程和代谢模型构建等最新技术来研究产甲烷菌的生化代谢过程以及其与其它菌群之间的相互作用机制,以便将其应用于生产实践.     

靛蓝的微生物合成研究新进展

靛蓝是一种广泛应用于印染、医药等行业的有机色素,利用微生物法合成靛蓝已引起国内外学者的广泛关注.本文综述了微生物法合成靛蓝的研究进展及动态.靛蓝的微生物合成可归纳为3个阶段:野生型微生物催化合成、基因工程菌全细胞催化转化及代谢工程调控转化.多数芳烃降解菌及其编码酶均具备催化吲哚合成靛蓝的能力,采用定向进化、宏基因组技术以及两相体系等对已知酶资源进行深尺度研究,将为靛蓝生物合成过程注入新的活力.同时,靛蓝合成过程中产生的羟基吲哚及靛蓝衍生物是新型药物及化工中间体,也具有较大的研究价值.然而,由于靛蓝合成过程涉及的中间产物及副产物间转化关系及合成脉络仍不明晰,靛蓝产率低,因此将分子生物学及代谢工程手段融入到靛蓝合成机理及产业化应用的探索将成为该方向的研究重点.     

西藏米拉山高寒草甸土壤微生物DNA提取及宏基因组Fosmid文库构建

青藏高原土壤中富含特殊的微生物资源,因大多数未能得到培养而无法利用.提取微生物总DNA及构建宏基因组文库的方法是研究未培养微生物的重要方法(免培养法).两藏米拉山高寒草甸土壤中腐植酸、有机质含量非常高,DNA提取非常困难,本研究表明卣接法提取该样品的DNA片段小,杂质含量高,不能满足构建大插入片段文库的要求;结合低速离心和Nycodenz密度梯度离心先分离出微生物细胞的间接法虽然DNA产率降低,但是纯度高,片段长,多样性丰富,更适合于构建大插入片段文库.在间接法提取高质量西藏高寒草甸土壤微生物DNA的基础上,成功构建了一个包含30 624个克隆、库容量超过1 Gb、稳定性好的宏基因组Fosmid文库,为从西藏高原土壤中挖掘和利用新的功能基因研究奠定了基础.图7表3参27     

南极中山站排污口土壤中微生物群落的DGGE分析

以南极中山站排污口土壤为研究对象,提取样品中微生物宏基因组DNA,用变性梯度凝胶电泳(DGGE)对宏基因组DNA中的16S rRNA基因V3可变区进行分析,测定了31个不同条带所代表的序列.比较结果显示,排污口土壤样品与相同生境对照样品中的微生物类群组成均以CFB (Cytophaga-Flexibacteria-Bacteroides)类群和γ-变形菌纲(γ-Proteobacteria)为主,另外还有少量的α-, β-, δ-变形菌纲,和一些原核的藻类和革兰氏阳性细菌(G ). 但在排污口土壤样品中检出了传染性微生物毛球菌属(Trichococcus)和狡诈菌属(Dolosigranulum),以及丰富的小球藻(Chlorella),说明污水的排放已经对该地微生物群落造成明显的影响.     

微生物还原Se(Ⅵ)和Se(Ⅳ)合成SeNPs机理研究新进展

硒(Se)是自然界中重要的元素之一,微生物在硒的生物地球化学循环中发挥着至关重要的作用.细菌、真菌及放线菌等多种微生物能够通过同化还原、异化还原等途径将Se(VI)和Se(IV)还原为硒纳米粒子(Se NPs).本文综述了目前已知的能够还原Se(VI)和Se(IV)的微生物资源及其还原机理,并总结了在硒化合物转运、Se NPs尺寸控制和稳定等过程中发挥重要作用的蛋白质和酶.微生物对Se(VI)的还原主要通过硒酸盐还原酶实现,而对Se(IV)的还原则通过包括亚硫酸盐还原酶、亚硝酸盐还原酶、谷胱甘肽和谷胱甘肽还原酶、硫氧还蛋白和硫氧还蛋白还原酶等多种酶促还原途径、非酶促还原途径以及作为电子受体参与的细胞呼吸过程来实现.多种不同的蛋白质和酶在Se(VI)和Se(IV)的跨膜转运、Se NPs的尺寸控制、稳定及外排等过程中发挥着重要的作用,它们不仅控制着硒化合物的还原过程,也会对Se NPs进行修饰从而改变Se NPs的物理化学性质,影响硒在环境中的归趋.今后仍需要不断开发新的能够代谢硒化合物的微生物资源,并结合基因组学、转录组学、蛋白组学等多种组学手段对微生物转化硒化合物的关键基因和调控系统等进行深入解析.     

锑和砷对固氮菌的毒性效应及其机制研究

锑作为一种具有毒性和致癌性的类金属,其不合理的开发造成了严重的生态环境污染,尤其是土壤中高浓度锑和砷污染导致了环境中多种营养元素的缺乏。其中,氮素的缺乏严重阻碍了环境的恢复。然而,固氮微生物不仅能为氮素匮乏环境提供稳定的氮素来源,而且其固氮潜能可以作为监测土壤金属污染的敏感指标。为此,该文通过乙炔还原法(ARA)微宇宙培养试验手段,研究了不同价态锑和砷(三价及五价)在不同质量浓度(100、200、500、1 000、2 500、5 000 mg·L^-1)水平下对棕色固氮菌固氮潜能的影响,同时进一步探究了土壤固氮菌群落固氮潜能对土壤中主要锑和砷价态[Sb(Ⅴ)和As(Ⅴ)]的响应机制。结果表明,锑和砷浓度与棕色固氮菌和土壤固氮微生物的固氮潜能均呈显著负相关,验证了以固氮微生物固氮潜能作为生物指示物的可行性。此外,Sb(Ⅴ)对土壤固氮微生物的毒性显著小于As(Ⅴ)。三价锑和砷污染对固氮菌固氮潜能的毒性高于五价[As(Ⅲ)>Sb(Ⅲ)>As(Ⅴ)>Sb(Ⅴ)],这可能是由于Sb(Ⅲ)和As(Ⅲ)对细胞的致裂性强于Sb(Ⅴ)和As(Ⅴ)。相较于Sb(Ⅴ)和As(Ⅴ)对于棕色固氮菌固氮潜能的抑制作用,其对土壤固氮菌群落的固氮潜能的影响相对较弱。这一差异可能是由于土壤复杂的理化性质以及微生物群落和功能多样性而导致的。     

大气颗粒物中微生物分析方法及分布特征的研究进展

大气颗粒物(particulate matter, PM)可能携带病原微生物,会对人体健康产生影响,因此,对大气颗粒物中微生物的采集和分析已成为当今的研究热点。本文对大气颗粒物中微生物的采集方法和分析方法(培养法、菌群多样性组成谱测序和宏基因组学技术)的研究进展进行简要概括,着重介绍不同条件下(区域、时间、粒径、天气条件和气象因素)大气颗粒物中微生物的分布状况差异,并对引起相关差异的原因进行了探讨,旨在为深入认识大气颗粒物中微生物的分布特征提供参考。     

不同浓度植物根系分泌物微生态效应研究

探讨夹竹桃(Nerium oleander)根系分泌物对土壤微生物量碳、呼吸强度等微生物学特征及土壤微生物群落功能多样性的影响,深入揭示夹竹桃根系分泌物的微生态效应,通过向土壤中添加植物根系分泌物溶液的方法,研究了不同浓度(CK,15 mL去离子水作为对照;LC,5 mL分泌物+10 mL去离子水;MC,10 mL分泌物+5 mL去离子水;HC,15 mL分泌物)的外源植物根系分泌物对土壤理化性质、土壤微生物群落功能多样性、微生物量碳、微生物熵、基础呼吸和代谢熵的影响。结果表明,不同浓度根系分泌物处理pH值显著低于CK(P<0.05);有机碳、含水量、全氮、碱解氮、速效磷含量显著高于CK(P<0.05),其大小表现为HC>MC>LC>CK;而土壤全磷无明显差异(P>0.05)。细菌、真菌、放线菌和微生物总数均显著高于对照(P<0.05),不同处理之间差异均显著(P<0.05),其大小表现为HC>MC>LC>CK。微生物量碳、微生物熵和基础呼吸均显著高于对照(P<0.05),不同处理之间差异均显著(P<0.05),其大小表现为HC>MC>LC>CK。土壤代谢熵表现为HC>MC>LC>CK,HC和MC差异不显著(P>0.05)。平均吸光值、物种丰富度指数、Mcintosh指数均显著高于对照(P<0.05),不同处理之间差异均显著(P<0.05),其大小表现为HC>MC>LC>CK。不同处理间优势度指数差异不显著(P>0.05)。主成分分析表明:中浓度根系分泌物处理的土壤与CK土壤微生物群落代谢特征相近,其明显不同于高浓度根系分泌物处理的土壤,说明它们对单一碳源的利用能力不同,其群落代谢特征存在差异。总体来看,高浓度的根系分泌物能够显著改变土壤微生物学特性及群落功能多样性。     

Water-dispersible nano-pollutions reshape microbial metabolism in type-specific manners: A metabolic and bacteriological investigation in Escherichia coli

• Water-dispersible nano-pollutions exhibit type-specific toxic effects on E. coli. • Global metabolite profiling was used to characterize metabolic disruption patterns. • Key dysregulated metabolites responsive to nano-pollution exposures were found. • Amino acid metabolism and purine metabolism are perturbed at nano-pollutions. Incomplete separation and recycling of nanoparticles are causing undesirable nanopollution and thus raising great concerns with regard to nanosafety. Since microorganisms are important regulator of physiological processes in many organisms, the interaction between nanopollution and microbial metabolomics and the resultant impact on the host’s health are important but unclear. To investigate how typical nanopollution perturbs microbial growth and metabolism, Escherichia coli (E. coli) in vitro was treated with six water-dispersible nanomaterials (nanoplastic, nanosilver, nano-TiO₂, nano-ZnO, semiconductor quantum dots (QDs), carbon dots (CDs)) at human-/environment-relevant concentration levels. The nanomaterials exhibited type-specific toxic effects on E. coli growth. Global metabolite profiling was used to characterize metabolic disruption patterns in the model microorganism exposed to different nanopollutants. The percentage of significant metabolites (p<0.05, VIP>1) accounted for 6%–38% of the total 293 identified metabolites in each of the nanomaterial-contaminated bacterial groups. Metabolic results also exhibited significant differences between different nanopollutants and dose levels, revealing type-specific and untypical concentration-dependent metabolic responses. Key metabolites responsive to nanopollution exposures were mainly involved in amino acid and purine metabolisms, where 5, 4, and 7 significant metabolic features were included in arginine and proline metabolism, phenylalanine metabolism, and purine metabolism, respectively. In conclusion, this study horizontally compared and demonstrated how typical nanopollution perturbs microbial growth and metabolomics in a type-specific manner, which broadens our understanding of the ecotoxicity of nanopollutants on microorganisms.     

Light quality effects on carbon metabolism and allocation in Gracilaria verrucosa

Under conditions of new nitrogen availability and low light intensities, light quality (blue, green, or red light) was not found to affect carbon fixation patterns into major metabolic fractions (total ethanol soluble, carbohydrate, and protein) in preconditioned nitrogen enriched or limited apical tips of Gracilaria verrucosa Papenfuss. Within the ethanol soluble fractions of both nitrogen enriched and limited tips, blue light treatment led to a greater percentage of ¹⁴ carbon in amino acids as compared to non-ninhydrin reactive metabolites. A lesser effect was observed with red light, and green light did not appear to stimulate amino acid synthesis appreciably. The low intensity blue light effect in G. verrucosa appears to be an enhancement of nonphotosynthetic carbon incorporation into amino acids, possibly through some form of the urea-ornithine cycle.Harbor Branch Foundation Contribution No. 237     

浙北典型稻作区近30年表层土壤碳氮含量变化

农业土壤碳库作为表生碳库的重要组成部分,对研究陆地生态系统碳循环具有重要意义。水稻土作为农业土壤的重要类型之一,其固碳能力研究对研究陆地生态系统碳循环具有现实意义。文章通过嘉善县20世纪80年代、2002年、2008年3次土壤调查数据,对嘉善县表层土壤中有机碳、氮含量及分布进行了分析,有机碳平均值在80年代到2002年呈下降趋势,2002—2008年微弱上升。全氮的平均值在80年代到2002年亦呈下降趋势,2002—2008年呈较快上升。以高密度网格化（1点/4km2）实测数据,计算得到2008年表层土壤有机碳、氮平均密度为44.36t·hm-2和5.3t·hm-2,平均容量为22.182kg·m-3和2.67kg·m-3,总储量分别为1.122×109kg和0.135×109kg,依据2002年、2008年两次可对比的实测数据,采用GIS和地统计学工具,进行了含量的空间分析,以1点/4km2精度,计算了2002—2008年县域内农用地表层土壤的有机碳、氮的变化。2002—2008年每年平均储碳速率为30.8kg·hm-2,储氮速率为156kg·hm-2。2002—2008年碳氮比平均值下降了2.3,依据土壤粒级数据和Hassink的碳保持容量公式,计算出嘉善县土壤平均固定容量为2.478%,初步估算,全县耕地表层土壤还具有42.43万t的固碳潜力,影响表土有机碳储汇的自然因素主要为土壤含水量和质地。     

Research progress and prospects of complete ammonia oxidizing bacteria in wastewater treatment

• Comammox bacteria have unique physiological characteristics. • Comammox bacteria are widely distributed in natural and artificial systems. • Comammox bacteria have the potential to reduce N₂O emissions. • Coupling comammox bacteria with DEAMOX can be promoted in wastewater treatment. • Comammox bacteria have significant potential for enhancing total nitrogen removal. Complete ammonia oxidizing bacteria, or comammox bacteria (CAOB), can oxidize ammonium to nitrate on its own. Its discovery revolutionized our understanding of biological nitrification, and its distribution in both natural and artificial systems has enabled a reevaluation of the relative contribution of microorganisms to the nitrogen cycle. Its wide distribution, adaptation to oligotrophic medium, and diverse metabolic pathways, means extensive research on CAOB and its application in water treatment can be promoted. Furthermore, the energy-saving characteristics of high oxygen affinity and low sludge production may also become frontier directions for wastewater treatment. This paper provides an overview of the discovery and environmental distribution of CAOB, as well as the physiological characteristics of the microorganisms, such as nutrient medium, environmental factors, enzymes, and metabolism, focusing on future research and the application of CAOB in wastewater treatment. Further research should be carried out on the physiological characteristics of CAOB, to analyze its ecological niche and impact factors, and explore its application potential in wastewater treatment nitrogen cycle improvement.     

Time-dependent metabolomics uncover dynamic metabolic adaptions in MCF-7 cells exposed to bisphenol A

● Metabolomic temporal profiling of cells exposed to xenobiotics. ● Global metabolome dysregulation patterns with time-resolved landscapes. ● Synchronized regulation behavior and specific dysregulation sensitivity. ● Temporal metabolic adaptions indicated cellular emphasis transition. The biochemical consequences induced by xenobiotic stress are featured in dose-response and time-resolved landscapes. Understanding the dynamic process of cellular adaptations is crucial in conducting the risk assessment for chemical exposure. As one of the most phenotype-related omics, metabolome in response to environmental stress can vary from seconds to days. Up to now, very few dynamic metabolomics studies have been conducted to provide time-dependent mechanistic interpretations in understanding xenobiotics-induced cellular adaptations. This study aims to explore the time-resolved metabolite dysregulation manner and dynamically perturbed biological functions in MCF-7 cells exposed to bisphenol A (BPA), a well-known endocrine-disrupting chemical. By sampling at 11 time points from several minutes to hours, thirty seven significantly dysregulated metabolites were identified, ranging from amino acids, fatty acids, carboxylic acids and nucleoside phosphate compounds. The metabolites in different pathways basically showed distinct time-resolved changing patterns, while those within the common class or same pathways showed similar and synchronized dysregulation behaviors. The pathway enrichment analysis suggested that purine metabolism, pyrimidine metabolism, aminoacyl-tRNA biosynthesis as well as glutamine/glutamate (GABA) metabolism pathways were heavily disturbed. As exposure event continued, MCF-7 cells went through multiple sequential metabolic adaptations from cell proliferation to energy metabolism, which indicated an enhancing cellular requirement for elevated energy homeostasis, oxidative stress response and ER-α mediated cell growth. We further focused on the time-dependent metabolite dysregulation behavior in purine and pyrimidine metabolism, and identified the impaired glycolysis and oxidative phosphorylation by redox imbalance. Lastly, we established a restricted cubic spline-based model to fit and predict metabolite’s full range dysregulation cartography, with metabolite’ sensitivity comparisons retrieved and novel biomarkers suggested. Overall, the results indicated that 8 h BPA exposure leaded to global dynamic metabolome adaptions including amino acid, nucleoside and sugar metabolism disorders, and the dysregulated metabolites with interfered pathways at different stages are of significant temporal distinctions.     

Ecological network and emergy analysis of urban metabolic systems: Model development,and a case study of four Chinese cities

Analysis of the structure and function of urban metabolic systems is an important goal of urban research. We used network pathways and network utility analysis to analyze the basic network structure of the urban metabolic system and the complex ecological relationships within the system, providing a new way to perform such research. Using four Chinese cities as examples, we developed an ecological network model of the urban metabolic system. By using network pathway analysis, we studied the changing relationships between metabolic length and the number of metabolic pathways, and between metabolic length and reachability. Based on the distribution of the number of metabolic pathways, we describe the basic structure and intercompartment relationships of the system. By using the sign distribution in the network utility matrix, we determined the ecological relationships and degree of mutualism between the compartments of the system. The basic components of the system consisted of the internal environment, the external environment, and the agricultural, industrial, and domestic sectors. With increasing metabolic length, the ecological relationships among the components of the system became more diverse, and the numbers of metabolic paths and their reachability improved. Although the basic network structure of the four cities was identical, the mutualism index differed. Beijing's mutualism index was superior to that of Shanghai, and much higher than those of Tianjin and Chongqing. By analyzing the structure and function of the urban metabolic system, we provide suggestions for optimizing the structure and adjusting the relationships, and propose methods for the application of ecological network analysis in future urban system research.     

Metabolism and elemental composition of a giant chaetognath Sagitta gazellae from the Southern Ocean

Oxygen consumption, ammonia excretion and phosphate excretion rates were measured on Sagitta gazellae Ritter-Zahony, in conjunction with body composition analyses (water, ash, carbon, hydrogen, nitrogen and phosphorus). Both water content (94.7% of wet weight) and ash content (53.0% of dry weight) recorded on S. gazellae were the highest and the lowest, respectively, among the chaetognath data being reported. Contents of carbon, hydrogen and nitrogen of S. gazellae were the lowest among published values of chaetognaths. Metabolic comparison with other chaetognaths living in similar subzero water temperature revealed reduced rates in S. gazellae, while no appreciable differences were seen in the metabolic quotients (O:N, N:P and O:P ratios). The O:N atomic ratios were 10.5 to 15.9 indicating protein oriented metabolism. Reduced metabolic activity of S. gazellae is not due to their body composition as calculated daily metabolic losses of body carbon (0.50%), body nitrogen (0.38) and body phosphorus (1.6%) were also found to be lower than respective values reported on other congeners and even those of other zooplankton living in the Antarctic waters.