What can affect the bacteria in your sink?

Posted on February 5, 2020   by Harry Ferguson and Dr Paz Aranega Bou

Each year, the Microbiology Society awards a number of grants that enable undergraduates to work on microbiological research projects during the summer vacation. Over the next few months, we’ll be posting a series of articles from members who were awarded Harry Smith Vacation Studentships this summer. This week is Harry Ferguson, a third year Biological Sciences student at the University of Southampton.

From the student: Harry Ferguson

The aims of the project were to characterize the culturable Gram-negative bacteria found in waste traps collected from a hospital; investigate the effects of adding and subsequently stopping the addition of non-water beverages to the microbial community; and to investigate the influence of said liquid on the ability of the communities to form biofilms.

I spent the first few weeks familiarizing myself with the pathogens present in the waste traps of the sink rig, and with the techniques used to identify them. This included sub-culturing – use of antibiotic disk diffusions – and a MALDI-TOF mass spectrometry machine to properly identify the communities present within the water supply. We then spent the last four weeks utilising mock IV fluid and other nutrients to test the impact of putting such nutrients into the environment. This included learning to sample the sink rig, as well as continued identification of the communities. We also took advantage of another experiment on the rig, to check whether the softness of the water had any impact on the types or speed of growth in the communities on our sinks. Finally, we made use of crystal violet attachment assays to check the biofilm forming capabilities of the communities we had in our sinks.

© Harry Ferguson

The sink rig used to investigate microbial populations


The results we saw were that, generally, there was a negligible impact of different nutrients upon the size and type of populations in the waste traps of our rig. This is interesting, as it runs counter to the assumption that an increase in nutrients provided by the 5% glucose IV fluid, we used would create a larger community, when in fact, it had little-to-no effect. Also, there was no significant difference between the community growth in soft and hard water, though the population types did shift slightly.

Unfortunately, due to the complex nature of the rig, we ran into some issues part way through the experiment. For this reason, we were forced to change the nature of the experiment from a moderate length experiment to a short-term study of the impacts of nutrients specifically. We also decided to make use of the change in water softness, to study whether that had any impact on our communities. Finally, due to time constraints– and the number of subcultures required to maintain a record of identification of all the species within each sink – we had to tone down the level of identification, focusing more on the general population size.

This work will form a foundation of knowledge about nutrient use in hospital sinks, and the data will be used to augment future studies using the rig.

This project has vastly increased my level of lab experience, to the point that I now feel very confident in my ability to carry out most tasks in a microbiology laboratory. I have gone from a student with less than 20 hours of lab experience, to having over 250 hours of experience in a working microbiology lab. Working at Porton Down also gave me insight into what I can expect from future research work and has left me excited to continue in the field.

From the supervisor: Dr Paz Aranega Bou

Harry had little experience in a microbiology lab at the start of the project. However, he had a great attitude from the beginning and he was able to pick up the techniques required. He also showed attention to detail, which is an essential skill for culturing polymicrobial communities. He understood the challenges of working with a complex model system and took responsibility for his own project (for example, providing daily nutrients to his sinks to maintain bacterial populations). Even more importantly, Harry has progressively acquired the ability to work independently in the lab without direct supervision. By the end of the project he was in control of all aspects of experimental work such as preparing the materials required, making decisions and conducting experiments. I was also impressed with his ability to interpret and discuss the results, and he is planning to submit an abstract to the Microbiology Society Annual Conference to present his results, which shows that the project has increased his interest in research and microbiology. He has also mentioned the intention to apply for other placement opportunities in the field of microbiology.

I am very grateful for this opportunity which has contributed to improve several aspects of my professional development. I first had the challenge of writing an application. I had to come up with a project that could be completed in two months and was suitable for a student. This made me realize the different things need to be considered when designing projects and helped me gain skills for grant application writing. Although I had contributed to student supervision in the past during my PhD, and have a lot of experience demonstrating in university laboratories; being Harry’s main supervisor was a completely different experience.

Even though Harry was a great student, it was challenging to be solely responsible for the project and him, but it was a good learning experience. Being somebody’s manager requires you to be more adaptable in the way you work, because you have to consider the other person’s priorities and ways of working. Receiving a Harry Smith Vacation Studentship was a great way of getting first-hand experience of supervising, as it was a short time commitment. It has helped me reflect on my leadership skills and how I need to further develop them for my future career.