By Lewis Hayward
The aim of my placement was to isolate a yeast (Metschnikowia pulcherrima) that is capable of producing an antibiotic from blackberry bushes found on campus. I collected 3 leaves, 3 fruits and 3 flowers from 5 bushes on Bath University’s Bee Unit. From there I had to compare yeasts growing on those three structures.
Taking cuttings from each leaf, I positioned them in the lid of a petri dish using the surface tension of water as an adhesive (since the petroleum jelly had run out). For each of the 3 leaves per location, one cutting was face up and the other face down. This was designed to compare the yeasts on the upper and lower surface. The idea was that the ballistospores would be fired onto the agar below. Unfortunately the surface tension was not enough to prevent them falling, so all the microorganisms from within the cuttings grew.
Mass of fruits and flowers were recorded for each location. For each location, the 3 fruits were placed in a tube of tropic soy broth. Flowers were treated the same. All tubes were shaken for 5hrs to dislodge yeast. Yeast solution was diluted and spread on agar. After a 48hr wait, I had to painstakingly count the yeast colonies and calculate an average. Luckily the desired yeast was distinguishable by its pinky/red colour. I was later able to transfer small amounts of yeast from selected colonies to fresh agar. I discovered that 26.6% of all yeast on fruit and 1.5% of all yeast on flower s was Metschnikowia.
I had the chance to make up a PCR solution containing water, primers and pre-prepared nucleotide solution. Once yeast was added to these, they were placed in the PCR machine. Electrophoresis was used to compare lengths of separated/uncoiled DNA strands to a ladder.
To test bacterial inhibition of various strains of Metsch., I took plugs from each and placed them in plates freshly inoculated with bacteria. A strain called ‘I48’ produced the largest zone of inhibition in the 1st batch.
The experience was genuinely great – a tool that allows one to undertake a real, in-context research task as well as providing insight into the working life of a scientist and finding out about others’ careers. It proves that sometimes repetition, contamination, errors and waiting are part of what it means to be a scientist. Absolutely worthwhile!