Microbial communities cycling organic sulfur compounds in Arctic sea ice

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. Changes in the Arctic are also likely affecting biological processes that lead to emission of biogenic volatiles that are precursors for secondary organic aerosols (SOA). Dimethylsulfide (DMS) is an organosulfur gas that plays an important role in SOA formation, cloud formation and climate feedbacks. The marine environment is the largest source for atmospheric DMS. 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. Most DMS is produced by enzymatic degradation of dimethylsulfoniopropionate (DMSP) by DMSP-lyases (Curson et al 2011). DMSP is an osmolyte produced 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 (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 threatened ecosystem.

Methodology
You will use a wide range of 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 in Norwich (https://www.uea.ac.uk/environmental-sciences/sea-ice-chamber), which will facilitate experimental work aimed at optimising approaches to study sea ice microorganisms.

Training and skills
CENTA students are required to complete 45 days training throughout their PhD including a 10-day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes. Your project specific training will include a wide range of approaches as required and could include microbial cultivation and characterisation, bacterial genetics, biochemistry, genomics, and studying the diversity and metabolic potential of environmental microbial communities using high throughput sequencing methods and metagenomics. You will also be trained in relevant analytic chemistry techniques such as gas and ion chromatography.