Microbiology Editor’s Choice: Varying Biofilm Hydrophobicity in Environmental Isolates of Bacillus subtilis 

Posted on October 25, 2021   by Microbiology Society

Each month, a manuscript published in our flagship journal Microbiology is chosen by a member of the Editorial Board. This month, the paper is titled ’Biofilm hydrophobicity in environmental isolates of Bacillus subtilis‘ and was chosen by Dr Jennifer Cavet.

Biofilm communities of bacteria attach to surfaces and are protected from environmental stresses by a self-produced extracellular matrix. A widely used model for studying biofilm formation is the Bacillus subtilis soil isolate, NCIB 3610, that forms complex and highly hydrophobic colony biofilms, with hydrophobicity being linked to the hydrophobin protein, BslA at the biofilm surface that provides increased biocide resistance.  

So far, knowledge of the mechanisms of B. subtilis biofilm production have mostly been gained from studies using the NCIB 3610 isolate, and the extent to which biofilm hydrophobicity is conserved within the B. subtilis species has remained unclear. This study addressed this by creating a library of B. subtilis environmental isolates, acquiring their whole genome sequences and examining biofilm colony hydrophobicity. Applaudably, a ‘citizen science’ approach, engaging members of a local community, was used to acquire the isolates from soil. Interestingly, the authors show that although all the isolates encode and produce BslA in mature biofilms, only a minority produce hydrophobic colonies. The lack of hydrophobicity is therefore, not associated with an inability to produce BslA, although the reason for the lack of uniformity in biofilm properties remains unclear.  

This study highlights that the properties of biofilms can vary for different isolates of the same species and hence the importance of using a diverse range of isolates as representatives of a species. This likely has implications not only for the study of biofilms but also for the study of bacterial systems generally.  

Biofilm hydrophobicity in environmental isolates of Bacillus subtilis 

Bacteria commonly live in communities called biofilms, where cells are surrounded by a self-produced extracellular matrix made up of proteins, DNA and sugars. An organism widely used for researching biofilms is Bacillus subtilis and in particular the isolate NCIB 3610. NCIB 3610 produces the protein BslA as part of its extracellular matrix, which makes the biofilm highly hydrophobic. Here, we tested if other soil isolates of B. subtilis are also hydrophobic and found that although all isolates produce BslA, only a few were water-resistant. The reason for the lack of hydrophobicity, despite BslA being produced, remains to be determined.  

We spoke with author Margarita Kalamara to find out more:  

What is your institution and how long have you been there? 

I am a third year PhD student based at the University of Dundee and I have been here since 2013 when I started my undergraduate degree. 

What is your research area? 

I study how environmental isolates of Bacillus subtilis behave in communities, both in single and mixed biofilms. 

What inspired you to research this topic? 

It is just super interesting! I did my undergraduate project in the same lab and found the topic of biofilm formation fascinating so I stayed to do a longer more in-depth research project for my PhD.  

What is the most rewarding part of your research? 

Seeing a project through from its first steps to publication and being part of an environment where knowledge and resources are continuously shared between group members.  

What would you be doing if you weren't a scientist? 

Probably something related to animal welfare.