Tuberculosis is one of the deadliest infectious diseases worldwide. As the treatment of it is inherently difficult due to the ability of the bacteria Mycobacterium tuberculosis to switch into a dormant state, in which the metabolism is nearly shut down, and no antibiotics can affect the bacteria, research on the cell cycle and metabolism is still needed. For this, M. smegmatis is widely used in research as it acts as a model organism for Mycobacterium tuberculosis. 

An MM is a microfluidic device fabricated through soft lithography. It is designed to trap and measure single bacteria. Hereby, long-term experiments enable the study of bacterial growth, cell cycle or the effect of toxins. An MM consists of a broad main channel and small dead-end side channels perpendicular to it. The main channel ensures nutrient supply, whereas the side channels trap single bacteria. As a bacterium at the end of a side channel continues growing, the progeny is pushed towards the main channel where it is flushed away. Using this concept, a constant number of bacteria under steady-state conditions is kept in a side channel and can be investigated.

In our project, bacteria are introduced into side channels where they are imaged via Raman spectroscopy to gain chemical information on a single cell level. Afterwards, the trapped bacteria are incubated using medium containing 50% D₂O. After 16 h of incubation, bacteria are measured again using Raman imaging. Consequently, the uptake of deuterated medium can be demonstrated by the detection of a C-D band in the spectrum. This proves the viability of the cells inside the MM. False-color images are used to display the ratio of deuterated and undeuterated components of the bacteria. This concept opens up possibilities to study cell cycles in long-term experiments or, for example the influence of antibiotics or toxins on cell growth or metabolism.