Unexpected sulfur cycling in terrestrial settings 

Lead Supervisor: Prof. Jon Todd 

Location: University of East Anglia, School of Biological Sciences

Duration: 8 weeks

Suitable undergraduate degrees: Microbiology, Molecular Biology or Biological Sciences 

Project background

Overview: Dimethylsulfoniopropionate (DMSP) is an abundant marine sulfur compound with roles in stress protection and biogeochemical cycling. Microbial DMSP cleavage releases the climate-cooling gas dimethylsulfide (DMS). Our new work shows: DMSP production is widespread in land plants; rhizosphere samples produce DMS from DMSP and house bacteria that cleave DMSP but lack known DMSP lyase genes.  

 Our new data implies: terrestrial DMSP cleavage is globally significant, yet we have little understanding of it; there are novel DMSP lyase enzymes to discover; and salination and drought associated with climate change may increase terrestrial DMSP and CAG levels.   

Here, functional genomics will be used to identify novel DMSP lyase enzymes in an agricultural soil Rhizobium isolate (U1) obtained on current NERC-funded research, which lacks known DMSP lyase genes. Physiological work will study how environmental conditions impact DMSP cleavage by this isolate. Data gleaned here will interest the wider scientific community, e.g., biogeochemists – enzymologists. 

The student will use previously successful methods to test 2 hypotheses: 

Hypothesis 1 – Rhizobium strain U1 (U1) utilises a novel DMSP lyase enzyme. 

Tasks: Use functional genomics to identify U1 genomic library clones with DMSP lyase activity. Use sequencing and bioinformatics to identify candidate DMSP lyase genes. Clone and test the activity of the candidate enzymes in E. coli.  

Hypothesis 2 – U1 DMSP lyase activity is influenced by the environment. 

Tasks: Grow U1 under varied conditions (designed by the student) and study its DMSP lyase activity by gas chromatography (GC) and lyase gene expression by RT-qPCR (time permitting).  

Feasibility: U1 has 2 day a growth cycle and previous genomic library screening always identified DMSP lyases within ~1000 clones. 

Expected outcomes: 

1. The student will gain valuable training in molecular microbiology, analytical GC work and microbial physiology. This is vitally important to the applicant for a potential molecular microbiology PhD in the future. 

1. Part 1 will identify a novel DMSP lyase enzyme in the model terrestrial bacterium, enabling important future work to investigate their biochemistry and enzymology, the significance of this system and of terrestrial DMSP cycling, which has been ignored in favour of marine settings. 

1. Part 2 will identify conditions that regulate DMSP lyase activity in terrestrial bacteria.  

1. Data will form the basis of a significant publication. 

This is a two tiered application process.  Initial applicant selection will be made by project supervisors and a further interview (online) will be conducted by UEA members of ARIES on the afternoon of Tuesday 13^th June.