Blog 1: The Secret Lives of Diatoms
This summer I’m lucky enough to be interning in a laboratory based at the École Normale Supérieure in Paris. The group research diatoms, which are microscopic, single-celled phytoplankton. Despite being unfamiliar to most people, they are ubiquitous in the earth’s aquatic habitats, and in contrast to their humble size are of enormous ecological importance, producing a fifth of the planet’s oxygen via their photosynthetic activity. Adding to this impressive list of credentials, they are also hugely diverse, with over 100,000 known species. Their role as big players in the global carbon chain, their dominance in aquatic ecosystems, and the diversity of environmental conditions they can inhabit makes them of great interest to scientists. In addition to their fundamental importance, they also look pretty cool. The fact that even closely-related species often form their external silicon skeletons differently means that a sample of diatom diversity appears a bit like the view through a kaleidoscope!
The lab I’m working with are particularly interested in diatom genomes – what we can learn about diatom physiology and evolution from sequencing their DNA. An aspect of their research that I am involved with focuses on the epigenetic processes regulating the genomes. ‘Epigenetics’ refers to chemical modifications of DNA itself and of the proteins (known as ‘histones’) that DNA is wrapped around for storage. Some types of modification cause sections of DNA to be more tightly wound up into histones, meaning that the sequence is far less readily accessible to the molecular machinery that reads it and translates it into a protein – and so any genes in that region of DNA are switched off.
I’ve been able to work with people using a wide variety of techniques to study diatom epigenetics. For instance, one approach involves fluorescently labelling different types of modification within the nucleus and imaging their distribution with a microscope. Doing so allows them to ask many interesting questions – for example, how do the epigenetic marks change under different environmental conditions, such as light and dark, or variation in temperature? Understanding this tells us something about how diatoms can adapt to changing environments by altering which genes are switched on. This is particularly interesting given that some diatoms can cope with fairly extreme changes, like being encased in ice for several months over winter, only to emerge perfectly happy and healthy when springtime comes around.
It’s been so useful to gain some insight into the research methods in this field and to learn some new techniques for myself – but ultimately what excites me about this internship is the chance to see how epigenetics, a relatively young but rapidly moving field of molecular biology, is relevant to understanding organisms at an ecological or evolutionary level. Diatoms occupy a position on the tree of life relatively far away from better-studied groups of organisms such as plants, animals and fungi, which allows us to explore which ways of regulating gene expression are shared by all of these creatures, and hence how these mechanisms evolved. Furthermore, because diatoms are so important ecologically, understanding how they function and adapt to different environments is crucial; more so now than ever what with climate change. So, by studying the nitty-gritty details of genome regulation in these unassuming but highly important creatures, we can gain some insight into much wider biological questions.
Blog 2 A Summer of Science in Paris: http://www.bangscience.org/2017/10/internship-at-ecole-normale-superieure-blog-2/