Archive for the ‘Symbiosis’ Category
With the global population approaching seven billion and showing no sign of slowing, it’s not surprising that governments are worried about food security. A future without genetically modified crops now seems impossible.
In one of the more exciting genetic modification projects, scientists at the John Innes Centre in Norwich are trying to engineer wheat that can produce its own fertiliser. There is also growing interest in understanding the role of soils and soil microbes in promoting plant growth, and we’ve written before about the role of antibiotic-producing bacteria in disease-suppressive soils.
Two recent high-profile papers report a more detailed analysis of the microbiomes found in the roots and rhizosphere (the soil touching the roots) of the model weed Arabidopsis. Both studies found that the phylum Actinobacteria was one of the three most dominant groups in plant roots, and most of these were Streptomyces bacteria (streptomycetes).
Microbiomes are the communities of microorganisms that live in, or on, host plants or animals. They are a subject quite literally close to our hearts (and every other major organ).
Over the past four years, the Human Microbiome Project has spent billions trying to define the species of bacteria that are associated with different parts of our bodies, known as the human reference microbiome. The researchers were looking for species that are consistent between humans, but what they actually discovered is that there is no such thing as a typical human microbiome. The bacteria living in your mouth could be very different to those living in my mouth, but they both do the same job. How could this be?
Ants are amazing insects, and fungus-growing ants are perhaps the most amazing of all. This group includes the leafcutter ants that you’ve probably seen on David Attenborough’s TV programmes, carrying carefully cut leaf fragments to their nests along well-defined trails in the rainforest. Millions of ants can be found within a single underground nest the size of a three-storey house. Brilliantly, and without using a single moving part, the nests are perfectly air conditioned – maintaining constant temperature and humidity.
“But wait,” I hear you cry. “This is all very well, but what does it have to do with microbiology?” Well, did you ever wonder what the ants do with the leaves that they so diligently carry through the jungle? They don’t eat them; instead, they strip the waxy coating from the surface of the leaf and feed the mashed-up leaf material to a symbiotic fungus that they grow in ‘gardens’ found within the colony.
This fungus is the sole food source for their colonies and has co-evolved with the ants over 50 million years, during which it has developed structures rich in sugars and fats that the ants harvest to feed to their larvae and queen.
We all love living things that glow in the dark, and scientists are no exception. Roger Tsien won a Nobel Prize in 2008 for discovering and developing green fluorescent protein and – perhaps even more excitingly – evil scientists turned mice fluorescent in a recent episode of the BBC television series Sherlock.
For animals that live in the blackness of the deep ocean, a little bit of bioluminescence goes a long way. For the squid Euprymna scolopes, this bioluminescence is generated by Vibrio fischeri bacteria that live within its light organ. The light organ is incredible, and it helps to hide the squid’s silhouette. This symbiosis is a win–win situation: the bacteria get housed and fed, and the squid gets a built-in cloaking device. Free-living bacteria also generate bioluminescence – but if they’re not in a symbiotic relationship, why do they bother?
For some reason, I’ve a real hankering for Japanese food at the moment. I’ve no idea why – perhaps it’s due to me going through some old photos from when I toured across the country visiting labs about ten years ago. In one of them, I’m standing underneath a large fibreglass puffer fish outside a restaurant (no, I’m not going to post it).
Puffer fish, in case you didn’t know, is quite the delicacy in many parts of Asia. In Japan, it’s known as fugu. I didn’t eat any, though. Why not? Well, the fish is one of the most poisonous animals in the world. It must be skilfully prepared, or it’s potentially lethal: a slight tingling of the lips, and it’s goodnight. Deaths are rare nowadays, but I didn’t want to take the risk. I try to avoid eating anything that might kill me (although I did once – and only once – eat a kebab).
Symbiotic relationships, where organisms of different species work together for mutual gain, have been studied extensively in numerous biological systems, but modern genomic techniques are revolutionising our understanding of how these interactions work at the molecular level. A recent paper by John McCutcheon and Carol von Dohlen has reported an interesting case of a ‘three-way symbiosis’ between the mealybug (Planococcus citri) – a significant pest of plants – and two species of bacteria.
This interaction shows a high level of metabolic complementarity: the genes for several amino acid biosynthetic pathways that are essential to the mealybug are spread across the genomes of the three different species. This makes the mealybug completely dependent on its bacterial symbionts.
We’re all used to taking antibiotics when we are ill, but did you know that plants use them too? New research from scientists in the Netherlands and USA published this month in Science has revealed that antibiotic-producing bacteria that live in the soil can protect plants roots from infection.
One of the most important new fields of biology is the study of microbiomes – communities of microorganisms that are closely associated with animals and plants. The human microbiome is vital to our health, with the microorganisms in our gut helping us to digest food, for example.
The trouble is, most of the bacteria and fungi that make up these microbiomes cannot be grown in a laboratory, as we simply don’t know the conditions in which they are able to grow. Thankfully with the rapid advancement of DNA and RNA sequencing technologies it is possible to identify the microbes without ever having to grow them – known as metagenomics.