Plant Cuttings

Has spring sprung yet?

It's not just humans waiting for Spring - recent research reveals that microbes are also looking forward to the new growth of plants.
Image: Roberta F./Wikimedia Commons.
Image: Roberta F./Wikimedia Commons.

The weather’s been so bad in the UK recently that I’m not sure if spring – ‘one of the four conventional temperate seasons, following winter and preceding summer’ – with its attendant promise of life reinvigorated, etc, has actually arrived or not. Let’s assume it has, but as we await the long-overdue blossom on the trees, look to the future with a spring-blossom-related item.

Ashley Shade et al. have uncovered successional changes in the microbial community associated with blossom of apple (Malus domestica). Whilst we may be used to terrestrial successions of land plants taking hundreds of years, in keeping with the fast-cycling times of microbes these six-stage apple successions took place during the 7-day lifespan of the studied flowers. This previously unknown floroplane community included a preponderance of members of the Deinococcus–Thermus phylum  (which include many species that are resistant to extreme radiation, as well as several thermophiles), and ‘TM7’ a so-called ‘candidate phylum’ (a major lineage of bacteria whose existence is known solely through environmental 16S r(ibosomal)RNA sequences, as to date no species has been grown in the lab). Together with the decoding of its genome, one hope for this unexpected insight into apple floral biology is that it will provide a basis for better disease management of this economically important fruit.

And hot on the heels of that research, Jonathan Leff and Noah Fierer have used similar techniques – culture-independent 16S rRNA gene pyrosequencing (which ‘by sequencing well-characterized hypervariable regions of genes such as 16S rRNA… sequence data provides… unambiguous and discriminatory information for microbial identification’) – to examine the microbiota of 11 store-bought ‘produce types’, which included fruit (yes, apple was one such) and vegetables (including mushrooms – are they strictly vegetables?). Demonstrating that the sampled fruit and veg harboured diverse bacterial communities – and the communities on each product were significantly distinct from one another – they conclude that ‘humans are exposed to substantially different bacteria depending on the types of fresh produce they consume with differences between conventionally and organically farmed varieties contributing to this variation’. Tantalisingly, differentiating between closely related taxa that may have pathogenic and non-pathogenic representatives was not an objective of that study (nor was adding to the discussion as to whether ‘organic’ or ‘conventional’ farmed produce might be ‘safer’ in this regard…).

So, an assessment of whether those produce-residing bacterial communities may impact human exposures to potential pathogens is awaited. But, until then, do remember to wash your fruit and veg before eating!