病毒感染影响宿主细胞代谢研究进展

作为专性的细胞内寄生物,病毒没有独立代谢的能力,因此完全依赖于宿主细胞的代谢机制。病毒利用宿主细胞代谢网络提供的能量和生物合成前体物质来驱动其复制、装配和释放。因此,病毒挟持宿主细胞代谢以实现自身的复制和增殖。此外,病毒还可以通过编码辅助代谢基因(auxiliary metabolic genes,AMGs)调控宿主的细胞代谢,影响碳、氮、磷、硫循环,参与微生物驱动的生物地球化学循环。本文主要从细胞葡萄糖代谢、谷氨酰胺代谢、脂肪酸代谢、病毒AMGs调控宿主代谢影响生物地球化学循环4个方面总结病毒感染对宿主核心代谢途径影响的研究,以期为深入理解病毒-宿主相互作用提供参考,也将为通过代谢干预治疗病毒性疾病提供一定的理论依据。     

噬藻体辅助代谢基因(AMGs)研究进展

噬藻体是一类广泛存在于海洋及淡水环境中以蓝藻为感染宿主的病毒,对蓝藻种群结构与多样性以及水生态环境具有重要的影响。噬藻体携带一系列与宿主新陈代谢相关的同源基因被称为辅助代谢基因。它们编码的蛋白在噬藻体感染蓝藻过程中,可参与宿主的光合作用、戊糖磷酸循环、营养物质摄取以及核苷酸生物合成等代谢活动。近年来,一些辅助代谢基因被作为噬藻体分子检测的靶标基因,并用于噬藻体遗传多样性及其与蓝藻间相互关系的研究。本文综述了国内外有关噬藻体辅助代谢基因的来源、生物学功能及其多样性等方面的研究进展。     

环境病毒的宿主鉴定技术进展

病毒是地球上丰度最高的微小生命粒子,通过调控宿主的群落结构、介导宿主死亡和参与水平基因转移等方式影响着生物地球化学循环和地球生命演化。近年来,宏基因组学的发展实现了在全球尺度上对环境病毒的大规模探索和研究,大量新的病毒基因组被发掘,病毒在全球生态过程和生物地球化学循环中的角色和贡献也得到进一步认知。病毒在环境中的重要作用是通过感染宿主实现的。然而,环境病毒的宿主鉴定工作远落后于环境病毒基因组测序研究。本文综述了目前病毒宿主鉴定的主要技术及其优缺点和应用场景,总结了病毒的宿主鉴定在病毒生态学研究和生物工程领域的重要价值,并初步展望了未来病毒宿主鉴定技术的发展方向。     

磷酸化病毒蛋白的生物学功能及形成机制

磷酸化是病毒蛋白常见的一种翻译后修饰,在调控病毒与宿主的代谢中起重要作用。生物体内的代谢活动与细胞内的信号转导密切相关,通过磷酸化和去磷酸化修饰可改变蛋白生物活性,从而调控胞内生物信号的传递。磷酸化修饰的病毒蛋白参与调控病毒复制、病毒增殖和病毒粒子装配等一系列病毒的代谢活动,同时也影响宿主细胞内的信号转导,抑制宿主基因组复制和表达。本文就病毒蛋白的磷酸化修饰位点、其生物学功能及磷酸化修饰的分子机制进行综述,为病毒感染性疾病的防控治疗及药物开发提供参考。     

病毒介导的海洋球石藻(Coccolithophores)鞘脂类代谢调控

海洋球石藻(Coccolithophores)是一种全球广泛分布且具有重要生态功能的真核浮游植物,有些种类是大洋和近岸常见的赤潮种。自然海域中,病毒感染是导致球石藻死亡和赤潮消亡的一个关键因素。基于一株海洋球石藻Emiliania huxleyi及其特异性裂解病毒全基因组测序注释的结果,研究者们发现病毒可能通过基因横向转移从宿主基因组中获取了一系列与鞘脂类代谢相关的关键酶基因,进而在一定程度上掌控了宿主鞘脂类代谢,大量合成、积累病毒性鞘脂类物质,并最终诱导宿主细胞以凋亡的形式死亡。因此,病毒介导的宿主鞘脂类代谢在调节病毒与宿主间相互作用中具有重要意义。本文着重综述海洋球石藻病毒与宿主间的基因横向转移、病毒介导的宿主鞘脂类代谢特点及其生态学意义,以期深入了解海洋球石藻病毒与宿主间复杂的相互作用关系。     

全基因组范围代谢网络的构建和最小基因组研究

全基因组范围代谢网络（genome-scale metabolic network,GSMN）的构建是合成生物学研究的一个重要研究手段。通过整合各种组学数据和借助计算机进行模拟分析,将基因型与表型的关系进行定量关联,从而为从全局的角度探索和揭示生物代谢机制,进而对生物进行合理的重新设计和工程改造提供了有效的框架。该方法在最小基因组研究中也有着突出的优势,通过计算机辅助的基因组最小化模拟与分析,能够系统鉴定微生物基因组基因的必需性。迄今为止,已有近百个基因组范围的代谢网络发表,覆盖的生物包括原核生物、真核生物和古生生物,并广泛应用于医药、能源、环境、工业和农业等多个领域,展现出了广阔的应用前景。将对全基因组范围代谢网络构建的方法、应用,特别是其在最小基因组研究中的应用作简要的综述。     

肠道微生物与人体健康研究进展

人类肠道中定居着许多对宿主有益的微生物,包括细菌、病毒、真核生物等,它们在肠道内能与其他微生物及免疫系统相互作用,对人体健康具有重要影响,被称为"被遗忘的器官",它们的基因组也被誉为人类的"第二基因组",与人体的能量代谢及物质代谢有关。本文总结了人体肠道中病毒、真核生物、细菌和宿主免疫系统的相互作用,微生物群的失衡可能导致的疾病如肥胖和克罗恩病等,以及微生物环境在人体内的成熟过程,期望有助于诊断和治疗与肠道微生物失衡相关的疾病。     

动物宿主——肠道微生物代谢轴研究进展

肠道中栖息着数量庞大且复杂多样的微生物菌群,在维持宿主肠道微环境稳态中发挥重要作用。微生物菌群可以利用宿主肠道的营养素,发酵产生代谢产物,与宿主机体形成宿主—微生物代谢轴(host-microbe metabolic axis)。该代谢轴既能影响营养素吸收和能量代谢,又可调控宿主各项生理过程。本文主要阐述宿主-肠道微生物代谢轴的概念、肠-肝轴、肠-脑轴、肠道微生物与宿主肠道代谢轴的互作以及对机体健康的影响。     

海洋氮循环过程及基于基因组代谢网络模型的预测

海洋氮循环在地球元素循环中充当着必不可少的角色。海洋氮循环是由一系列氧化还原反应构成的生物化学过程。固氮作用和氮同化作用为生态系统提供了生物可用氮(铵盐)。硝化作用可进一步将铵盐氧化为硝酸盐,硝酸盐又可以通过反硝化作用转化为氮气。整个氮循环实现了海洋中不同含氮无机盐间的转换。微生物是海洋氮循环的重要驱动者,海洋氮循环的研究可以帮助理解海洋生物与地球环境相互作用及协同演化的机制,从而更好地保护地球生态环境。随着氮循环关键微生物基因组尺度代谢网络模型的发表,研究者可以利用代谢网络模型来研究不同氮循环过程的效率、环境因子对氮循环过程的影响以及解析氮循环及生物网络的内在机理等,从而帮助人们更深入地研究海洋氮转化机制。本文主要综述了海洋氮循环过程中各个转化过程的主要微生物,以及基因组尺度代谢网络模型在分析氮循环中的应用。     

人体肠道微生物多样性和功能研究进展

人体肠道中庞大而复杂的微生物群落对人体自身代谢表型有深远的影响.肠道微生物群落在亚种或菌株水平上表现出极大的多样性.利用微生物分子生态学、元基因组学和代谢组学研究方法,发现肠道微生物与宿主表现出共进化的特点,肠道微生物群落及其基因组为宿主提供了互补的遗传和代谢功能,表现出互惠共生关系.但是,肠道微生物群落中影响宿主代谢表型的关键功能菌鉴定及其作用模式问题仍然悬而未决,综合运用多种高通量研究方法和多维数据分析方法可能成为解决这个问题的突破口.     

Deep sea sediments associated with cold seeps are a subsurface reservoir of viral diversity

In marine ecosystems, viruses exert control on the composition and metabolism of microbial communities, influencing overall biogeochemical cycling. Deep sea sediments associated with cold seeps are known to host taxonomically diverse microbial communities, but little is known about viruses infecting these microorganisms. Here, we probed metagenomes from seven geographically diverse cold seeps across global oceans to assess viral diversity, virus–host interaction, and virus-encoded auxiliary metabolic genes (AMGs). Gene-sharing network comparisons with viruses inhabiting other ecosystems reveal that cold seep sediments harbour considerable unexplored viral diversity. Most cold seep viruses display high degrees of endemism with seep fluid flux being one of the main drivers of viral community composition. In silico predictions linked 14.2% of the viruses to microbial host populations with many belonging to poorly understood candidate bacterial and archaeal phyla. Lysis was predicted to be a predominant viral lifestyle based on lineage-specific virus/host abundance ratios. Metabolic predictions of prokaryotic host genomes and viral AMGs suggest that viruses influence microbial hydrocarbon biodegradation at cold seeps, as well as other carbon, sulfur and nitrogen cycling via virus-induced mortality and/or metabolic augmentation. Overall, these findings reveal the global diversity and biogeography of cold seep viruses and indicate how viruses may manipulate seep microbial ecology and biogeochemistry.Subject terms: Environmental microbiology, Microbial ecology     

Underexplored viral auxiliary metabolic genes in soil: Diversity and eco-evolutionary significance

Bacterial viruses are the most abundant biological entities in soil ecosystems. Owing to the advent of metagenomics and viromics approaches, an ever-increasing diversity of virus-encoded auxiliary metabolic genes (AMGs) have been identified in soils, including those involved in the transformation of carbon, phosphorus, and sulfur, degradation of organic pollutants, and antibiotic resistance, among other processes. These viral AMGs can alter soil biogeochemical processes and metabolic activities by interfering with bacterial host metabolism. It is recognized that viral AMGs compensate for host bacterial metabolism outputs by encoding accessory functional genes and are favourable for the hosts' adaptation to stressed soil environments. The eco-evolutionary mechanisms behind this fascinating diversity of viral AMGs in soil microbiomes have begun to emerge, such as horizontal gene transfer, lytic-lysogenic conversion, and single-nucleotide polymorphisms. In this mini-review, we summarize recent advances in the diversity and function of virus-encoded AMGs in the soil environment, especially focusing on the evolutionary significance of AMGs involved in virus-host interactions. This mini-review also sheds light on the existing gaps and future perspectives that could have major significance for viral AMGs research in soils.     

Viral elements and their potential influence on microbial processes along the permanently stratified Cariaco Basin redoxcline

Little is known about viruses in oxygen-deficient water columns (ODWCs). In surface ocean waters, viruses are known to act as gene vectors among susceptible hosts. Some of these genes may have metabolic functions and are thus termed auxiliary metabolic genes (AMGs). AMGs introduced to new hosts by viruses can enhance viral replication and/or potentially affect biogeochemical cycles by modulating key microbial pathways. Here we identify 748 viral populations that cluster into 94 genera along a vertical geochemical gradient in the Cariaco Basin, a permanently stratified and euxinic ocean basin. The viral communities in this ODWC appear to be relatively novel as 80 of these viral genera contained no reference viral sequences, likely due to the isolation and unique features of this system. We identify viral elements that encode AMGs implicated in distinctive processes, such as sulfur cycling, acetate fermentation, signal transduction, [Fe–S] formation, and N-glycosylation. These AMG-encoding viruses include two putative Mu-like viruses, and viral-like regions that may constitute degraded prophages that have been modified by transposable elements. Our results provide an insight into the ecological and biogeochemical impact of viruses oxygen-depleted and euxinic habitats.Subject terms: Microbial ecology, Metagenomics     

Potential virus-mediated nitrogen cycling in oxygen-depleted oceanic waters

Viruses play an important role in the ecology and biogeochemistry of marine ecosystems. Beyond mortality and gene transfer, viruses can reprogram microbial metabolism during infection by expressing auxiliary metabolic genes (AMGs) involved in photosynthesis, central carbon metabolism, and nutrient cycling. While previous studies have focused on AMG diversity in the sunlit and dark ocean, less is known about the role of viruses in shaping metabolic networks along redox gradients associated with marine oxygen minimum zones (OMZs). Here, we analyzed relatively quantitative viral metagenomic datasets that profiled the oxygen gradient across Eastern Tropical South Pacific (ETSP) OMZ waters, assessing whether OMZ viruses might impact nitrogen (N) cycling via AMGs. Identified viral genomes encoded six N-cycle AMGs associated with denitrification, nitrification, assimilatory nitrate reduction, and nitrite transport. The majority of these AMGs (80%) were identified in T4-like Myoviridae phages, predicted to infect Cyanobacteria and Proteobacteria, or in unclassified archaeal viruses predicted to infect Thaumarchaeota. Four AMGs were exclusive to anoxic waters and had distributions that paralleled homologous microbial genes. Together, these findings suggest viruses modulate N-cycling processes within the ETSP OMZ and may contribute to nitrogen loss throughout the global oceans thus providing a baseline for their inclusion in the ecosystem and geochemical models.Subject terms: Virus-host interactions, Biogeochemistry, Microbial biooceanography, Microbial ecology     

Depth-stratified functional and taxonomic niche specialization in the ‘core' and ‘flexible' Pacific Ocean Virome

Microbes drive myriad ecosystem processes, and their viruses modulate microbial-driven processes through mortality, horizontal gene transfer, and metabolic reprogramming by viral-encoded auxiliary metabolic genes (AMGs). However, our knowledge of viral roles in the oceans is primarily limited to surface waters. Here we assess the depth distribution of protein clusters (PCs) in the first large-scale quantitative viral metagenomic data set that spans much of the pelagic depth continuum (the Pacific Ocean Virome; POV). This established ‘core'' (180 PCs; one-third new to science) and ‘flexible'' (423K PCs) community gene sets, including niche-defining genes in the latter (385 and 170 PCs are exclusive and core to the photic and aphotic zones, respectively). Taxonomic annotation suggested that tailed phages are ubiquitous, but not abundant (<5% of PCs) and revealed depth-related taxonomic patterns. Functional annotation, coupled with extensive analyses to document non-viral DNA contamination, uncovered 32 new AMGs (9 core, 20 photic and 3 aphotic) that introduce ways in which viruses manipulate infected host metabolism, and parallel depth-stratified host adaptations (for example, photic zone genes for iron–sulphur cluster modulation for phage production, and aphotic zone genes for high-pressure deep-sea survival). Finally, significant vertical flux of photic zone viruses to the deep sea was detected, which is critical for interpreting depth-related patterns in nature. Beyond the ecological advances outlined here, this catalog of viral core, flexible and niche-defining genes provides a resource for future investigation into the organization, function and evolution of microbial molecular networks to mechanistically understand and model viral roles in the biosphere.     

Organochlorine contamination enriches virus-encoded metabolism and pesticide degradation associated auxiliary genes in soil microbiomes

Viruses significantly influence local and global biogeochemical cycles and help bacteria to survive in different environments by encoding various auxiliary metabolic genes (AMGs) associated with energy acquisition, stress tolerance and degradation of xenobiotics. Here we studied whether bacterial (dsDNA) virus encoded AMGs are enriched in organochlorine pesticide (OCP) contaminated soil in China and if viral AMGs include genes linked to OCP biodegradation. Using metagenomics, we found that OCP-contaminated soils displayed a lower bacterial, but higher diversity of viruses that harbored a higher relative abundance of AMGs linked to pesticide degradation and metabolism. Furthermore, the diversity and relative abundance of AMGs significantly increased along with the severity of pesticide contamination, and several biodegradation genes were identified bioinformatically in viral metagenomes. Functional assays were conducted to experimentally demonstrate that virus-encoded L-2-haloacid dehalogenase gene (L-DEX) is responsible for the degradation of L-2-haloacid pesticide precursors, improving bacterial growth at sub-inhibitory pesticide concentrations. Taken together, these results demonstrate that virus-encoded AMGs are linked to bacterial metabolism and biodegradation, being more abundant and diverse in soils contaminated with pesticides. Moreover, our findings highlight the importance of virus-encoded accessory genes for bacterial ecology in stressful environments, providing a novel avenue for using viruses in the bioremediation of contaminated soils.Subject terms: Metagenomics, Soil microbiology, Microbial ecology

As the most abundant biological entities on earth, viruses of bacteria (bacteriophages referred as viruses from here on) play a critical role in modulating the ecology of microbial communities through lytic infection and lysogenic conversion of their bacterial hosts [1, 2]. Viruses significantly influence the biogeochemical cycles via the release of organic carbon and nutrients through host cell lysis, and in addition to core viral genes (i.e., genes encoding viral structural proteins [3]), they also encode various auxiliary metabolic genes (AMGs [4, 5]), which contribute the metabolic capacity and survival of their bacterial hosts. The role of AMGs has been especially well demonstrated with marine viruses that encode a diversity of AMGs involved in photosynthesis [6], translation machinery [7], carbon metabolism [8], phosphate metabolism [9] and sulfur cycle [10, 11]. Furthermore, sequencing of whole marine viral communities has revealed a clear involvement of viral AMGs in central carbon metabolism of host bacteria [10, 12]. Compared with the study of viral communities in marine ecosystem, the diversity and functional role of viral AMGs in soils are less well understood.In soils, viruses reach abundances of up to ~10⁹ per gram of soil leading to frequent encounters with their host bacteria [13]. Similar to aquatic environments, viruses can regulate host bacterial densities, leading to indirect changes in the relative abundance of non-target bacterial taxa likely via release of niche space [14, 15]. Moreover, over longer time periods, viruses can coevolve with their host, following fluctuating selection dynamics [16] or patterns of local adaptation [17]. Viruses are also important mediators of horizontal gene transfer, promoting the transfer of antibiotic resistance genes, virulence factors and AMGs [18, 19]. However, these effects are less well understood at viral community level. Recent advances in viral purification have enabled a glimpse into soil viral communities of permafrost peatland [20, 21] and agricultural ecosystems [22, 23] based on metagenomics. These studies have demonstrated that viruses may alter the biogeochemical nutrient cycling [1, 2] and bacterial adaptation and evolution by carrying genes linked to carbon and nitrogen metabolism [20, 21]. Moreover, recent identification of atrazine chlorohydrolase trzN [24] and arsenic methyltransferase arsM [25] genes in soil-associated lysogenic viruses suggest that virus-encoded AMGs could shape bacterial metabolism under pollutant exposure. Therefore, we hypothesize, that contaminated soil microbiomes could contain a relatively higher abundance of viruses carrying AMGs linked to the degradation of pesticides and xenobiotics due to their potential benefit for the host bacteria.Pesticide contamination imposes a serious threat to natural ecosystems and public health globally. China is the leading producer of organochlorine pesticides (OCPs), which are synthetic pesticides with vast applications in chemical and agricultural industries. OCPs are especially notorious due to their high toxicity, slow degradation and bioaccumulation [26]. Following the implementation of the Stockholm Convention, hundreds of pesticide plants in China were closed or re-located, and contaminated soils around the plants left untreated. As microbial communities are often capable of degrading OCPs, there is growing biotechnological interest to identify important genes and microbial taxa behind pesticide biodegradation. Heavy OCP contaminations have previously been shown to adversely impact soil bacterial diversity, composition, and activity [27, 28]. Prolonged exposure to contaminants has resulted in selection for bacteria that have evolved their own degradation enzymes, such as dehalogenases, which protect from the toxic effects of pesticides [29]. Interestingly, if also viruses can carry and encode such genes, pesticide exposure could create a strong positive selection for virus-encoded AMGs associated with pesticide degradation, potentially shifting soil microbiome community composition [30] by favoring bacterial and virus taxa that carry these genes.To address this, we used a combination of metagenomics and direct experimentation to explore how pesticide exposure affects the abundance and type of bacterial and virus-encoded AMGs in the soil of former OCP production factory in Yangtze River Delta (China). We found that contaminated and clean control soils harbored very distinct bacterial and viral communities, and crucially, pesticide exposure was linked to higher diversity and abundance of virus-encoded metabolism and pesticide degradation AMGs. The functional activity of one candidate viral AMG, L-2-haloacid dehalogenase (L-DEX), was experimentally shown to improve bacterial growth at sub-inhibitory concentrations of haloacid, which is an important precursor of herbicides and insecticides. Together, our findings suggest that virus-encoded auxiliary genes could help bacteria to counteract pesticide stress, potentially explaining the benefits of virus carriage in stressful soil microbiomes.     

Viral community analysis in a marine oxygen minimum zone indicates increased potential for viral manipulation of microbial physiological state

Microbial communities in oxygen minimum zones (OMZs) are known to have significant impacts on global biogeochemical cycles, but viral influence on microbial processes in these regions are much less studied. Here we provide baseline ecological patterns using microscopy and viral metagenomics from the Eastern Tropical North Pacific (ETNP) OMZ region that enhance our understanding of viruses in these climate-critical systems. While extracellular viral abundance decreased below the oxycline, viral diversity and lytic infection frequency remained high within the OMZ, demonstrating that viral influences on microbial communities were still substantial without the detectable presence of oxygen. Viral community composition was strongly related to oxygen concentration, with viral populations in low-oxygen portions of the water column being distinct from their surface layer counterparts. However, this divergence was not accompanied by the expected differences in viral-encoded auxiliary metabolic genes (AMGs) relating to nitrogen and sulfur metabolisms that are known to be performed by microbial communities in these low-oxygen and anoxic regions. Instead, several abundant AMGs were identified in the oxycline and OMZ that may modulate host responses to low-oxygen stress. We hypothesize that this is due to selection for viral-encoded genes that influence host survivability rather than modulating host metabolic reactions within the ETNP OMZ. Together, this study shows that viruses are not only diverse throughout the water column in the ETNP, including the OMZ, but their infection of microorganisms has the potential to alter host physiological state within these biogeochemically important regions of the ocean.Subject terms: Microbial biooceanography, Microbial ecology     

Viral serine/threonine protein kinases

Phosphorylation represents one the most abundant and important posttranslational modifications of proteins, including viral proteins. Virus-encoded serine/threonine protein kinases appear to be a feature that is unique to large DNA viruses. Although the importance of these kinases for virus replication in cell culture is variable, they invariably play important roles in virus virulence. The current review provides an overview of the different viral serine/threonine protein kinases of several large DNA viruses and discusses their function, importance, and potential as antiviral drug targets.     

Identification of the Microbial Community Structure and Potential Mechanism of Environmental Adaptation in Contaminated Environments

Purpose: To assess the bacterial community structure and the possible mechanism underlying the environmental adaption in contaminated habitats.Methods: The 60-mer oligonucleotide multibacterial microarray (GSE38004) was downloaded from the Gene Expression Omnibus database. The changes in the abundance of bacterial populations and genes in contaminated habitats were assessed based on the gene expression profiles. Then the potential function of the genes and their involved pathways were predicted by a bioinformatics approach.Results: A total of 25 bacterial populations had different abundance between contaminated habitats and uncontaminated area, of which Sphingobium herbicidovorans (S. herbicidovorans) and Pseudomonas pavonaceae (P. pavonaceae) involved in 23 populations were determined to have higher abundance in contaminated areas. Additionally, 184 genes involved in anaerobic respiration and cellular respiration were detected to have potential bioremediation. The genes of MDH (Mannitol-1-phosphate/altronate dehydrogenases) and fadE (acyl-CoA dehydrogenase) may play key roles in the mechanism of metabolic adaption.Conclusions: S. herbicidovorans and P. pavonaceae were the predominant bacterial groups in contaminated sites for the various metabolic potential and antibiotic resistances. The significant genes (MDH, fadE) and pathways (citrate cycle, pyruvate metabolism, fatty acid metabolism) played key roles in the adaptive response of microorganisms in contaminated environment.     

The roles of polyamines in microorganisms

Polyamines are small polycations that are well conserved in all the living organisms except Archae, Methanobacteriales and Halobacteriales. The most common polyamines are putrescine, spermidine and spermine, which exist in varying concentrations in different organisms. They are involved in a variety of cellular processes such as gene expression, cell growth, survival, stress response and proliferation. Therefore, diverse regulatory pathways are evolved to ensure strict regulation of polyamine concentration in the cells. Polyamine levels are kept under strict control by biosynthetic pathways as well as cellular uptake driven by specific transporters. Reverse genetic studies in microorganisms showed that deletion of the genes in polyamine metabolic pathways or depletion of polyamines have negative effects on cell survival and proliferation. The protein products of these genes are also used as drug targets against pathogenic protozoa. These altogether confirm the significant roles of polyamines in the cells. This mini-review focuses on the differential concentrations of polyamines and their cellular functions in different microorganisms. This will provide an insight about the diverse evolution of polyamine metabolism and function based on the physiology and the ecological context of the microorganisms.