Microbiology of Salt Marshes in the UK: Insights into Life in Gradient-Rich Environments


Student thesis: Doctoral Thesis


Gradual changes in physico-chemical factors occurring along spatial and temporal scales in different ecosystems are described as environmental gradients. Salt marshes, an example of such gradient-rich environments, are intertidal marshy zones characterised by continuous alternating tidal cycles. Such dynamic environments are suitable hotspots for studying microbial biodiversity. The microbes of these environments could be fruitful ecological or biotechnological resources of bioactive agents that remain functional even in extreme conditions, although there are only a limited number of cultured microbes described from salt marsh environments including those in the UK. Thus, the scientific and economic value of most of these marsh sites has largely remained unexplored.

This study aimed to explore culturable diversity, and novel and potentially beneficial microbes within salt marshes, alongside the development of a promising and rapid technique for the cultivation of microbes from gradient-rich environments. Samples were obtained from salt marshes at RSPB Marshside and Fingringhoe Wick Nature Reserve, situated at the geographically and climatically distinct North-West and South-East regions of England. Pure microbial isolates obtained via cultivation-based analysis were cryopreserved, phylogenetically identified using their 16S rRNA genes, and screened for novel species as well as antimicrobial production. A full characterisation of two of the novel isolates was performed through polyphasic tests and draft genome analysis. Additionally, based on the diffusion concept, 'gel-stabilised gradient plates' were developed to mimic the physico-chemical components of gradient-rich ecosystems.

This combined approach of cultivation- and molecular-based studies with biotechnological screening identified the cultivable microbial diversity and made the initial steps to describe this diversity in the salt marshes of the UK. The present study additionally suggested the antimicrobial production by the isolates and discovered the novel microbes Halomonas aestuarensis and Pseudoalteromonas belisamaea isolated from study marsh sites. The gel-stabilised gradient plate also confirmed its significance in direct and wider applications in microbial culturing.
Date of Award27 Jul 2021
Original languageEnglish
Awarding Institution
  • Edge Hill University
SupervisorJAYNE CHARNOCK (Director of Studies), PAUL ASHTON (Supervisor) & André Antunes (Supervisor)


  • Environmental gradients
  • Salt marshes
  • Microbial cultivation
  • Microbial isolation
  • Gradient-plate diffusion

Cite this