Microbial communities cycling organic sulfur compounds in Arctic sea ice

概述由于气候变暖，北极正在经历重大变化。北极冰盖对区域和全球气候具有重要的反馈和调节功能，但最近北冰洋的冰盖范围已降至创纪录的低水平(Notz和Stroev2016)。北极的变化还可能影响导致生物挥发性化合物排放到大气中的生物过程，这些挥发性化合物是二次有机气溶胶的前体，作为云形成的粒子发挥重要作用并提供气候反馈(Carpenter等人，2012)。海洋环境是大气DMS的最大来源(Lana等人，2011年)。可以排放到大气中的二甲基硫的量与推动其生产和降解的微生物活动有关。这些复杂的有机硫化合物循环途径由一系列不同的酶和微生物群驱动(图1)。大多数DMS是通过DMSP裂解酶对DMSP的酶降解产生的(Curson等人，2011年)。DMSP是一种渗透分子，每年由一系列浮游植物、冰藻和我们所示的各种海洋细菌以千万亿克的数量产生(Ksionzek等人，2017年)。细菌对DMSP总产量的贡献还不是很清楚。二甲基硫可被甲基营养细菌用作碳源(Neufeld等人2007年，Schäfer等人2007年，Schäfer等人2010年)，或者如最近在Warwick会议上显示的那样，DMS可被异养细菌共氧化成二甲基亚砜(DMSO)(Lidbury等人2016年)。DMSP和DMS的降解也可以涉及甲硫醇的产生，甲硫醇在细菌中被甲硫醇氧化酶降解(Eyice等人，2018年)，或者可以重新甲基化生成DMS(Carrión等人，2015年)。2019年，我们将参与多学科马赛克行动(https://www.mosaic-expedition.org/)，)，该行动将在北极海冰部署一艘破冰船，为期一整年，对北极进行前所未有的详细研究。马赛克是一个从北极获取样本并调查这个受到气候变化威胁的生态系统中硫循环微生物的机会。方法您将使用广泛的实验和分析方法，包括微生物学、分子生物学和生物信息学方法，从北极样品和实验海冰微观世界中分离和鉴定微生物和微生物群落。工作可能包括生理特征、基因组测序以及对分离的微生物进行潜在的遗传分析。您将基于高通量测序方法(扩增子测序)以及项目中提出的样本的元基因组学来分析微生物群落的组成和功能。一个令人兴奋的机会是在UEA提供了一个冰室，这将促进旨在优化研究海冰微生物的方法的实验工作。传统上，这涉及到海冰的缓慢融化，这会改变化学环境，并可能改变冰上微生物的生理状态。因此，需要开发将这种变化降至最低的方法，然后将其应用于研究冰微生物在冻结/融化周期中的反应。

Overview The Arctic is undergoing significant changes due to climate warming. Arctic ice cover has significant feedbacks and regulatory function for regional and global climate, but recently the extent of ice cover in the Arctic Ocean has fallen to record low levels (Notz and Stroeve 2016). Changes in the Arctic may also affect biological processes that lead to emission of biogenic volatile compounds into the atmosphere, which are precursors for secondary organic aerosols (SOA) that play important roles as particles for cloud formation and provide climate feedbacks (Carpenter et al 2012).Dimethylsulfide (DMS) is an organosulfur gas with a role in SOA formation. The marine environment is the largest source for atmospheric DMS (Lana et al 2011). The amount of DMS that can be emitted to the atmosphere is linked to microbial activities driving its production and degradation. These complex pathways of organosulfur compound cycling are driven by a wide range of different enzymes and microbial groups (Figure 1). Most DMS is produced by enzymatic degradation of dimethylsulfoniopropionate (DMSP) by DMSP-lyases (Curson et al 2011). DMSP is an osmolyte produced in petagram quantities (Ksionzek et al 2016) per year by a range of phytoplankton, ice algae and, as shown by us, diverse marine bacteria (Curson et al 2017). The bacterial contribution to overall DMSP production is not well understood. DMS can be used as a carbon source by methylotrophic bacteria (Neufeld et al 2007, Schäfer 2007, Schäfer et al 2010) or as recently shown at Warwick, can be co-oxidised by heterotrophic bacteria to dimethylsulfoxide (DMSO) (Lidbury et al 2016). Both DMSP and DMS degradation can also involve the production of methanethiol (MT), which is degraded in bacteria by methanethiol oxidase (Eyice et al 2018), or which can be re-methylated to produce DMS (Carrión et al 2015). In 2019, we will participate in the multidisciplinary MOSAiC campaign (https://www.mosaic-expedition.org/), which will deploy an ice breaker in Artic sea ice for an entire year to study the Arctic in unprecedented detail. MOSAiC is an opportunity to obtain samples from the Arctic and investigate sulfur cycling microorganisms in this ecosystem threatened by climate change. MethodologyYou will use a wide range of experimental and analytical approaches, including microbiological, molecular biological and bioinformatic methods to isolate and characterise microorganisms and microbial communities from Arctic samples and experimental sea ice microcosms. Work may include physiological characterisation, genome sequencing and potentially genetic analysis of isolated microorganisms. You will analyse microbial community composition and function based on high throughput sequencing approaches (amplicon sequencing) as well as metagenomics of samples raised in the project. An exciting opportunity is the availability of an ice chamber at UEA, which will facilitate experimental work aimed at optimising approaches to study sea ice microorganisms. Traditionally, these involve slow melting of sea ice, which alters the chemical environment and potentially the physiological state of ice-dwelling microbes. Hence, methods that minimise such changes need to be developed, which could then be applied to study the response of ice microbes during freeze/thaw cycles, for instance.