Growing organisms on plates is perhaps the most rudimentary analysis technique for studying growth rates and the interactions between organisms. The process is time consuming since the formation of colonies for most organisms takes days. Further, if colony counting is performed by hand (rather than using some software or other tool) yet more time is taken to obtain results. Moreover, the number of colony forming units found by colony counting is not necessarily representative of the number of organisms with which the plate was inoculated. There is no way of reliable ascertaining information about the intermediary growth stages of the organism(s) in question using this method.

While staining and observing cells under an optical microscope is not so time consuming as the above plating method, it has its own limitations. In order to prepare samples and record data, someone must be present at all times. This is not true of the design of our Quicker Way to Analyse Co-Cultures (QWACC) system. (That is, the combined upright DIHM and milli-fluidic chamber.) Although, as our Results suggest, we had some trouble getting everything to work simultaneously, we firmly believe that the design is capable of carrying out automated co-culture analysis with relatively little change. Further, we need not remove samples from our cultures or stain them, meaning a less time-consuming process with fewer opportunities for contamination and no need for a person's constant presence.

We used this as the gold-standard for accuracy in our tests. We compared our results with the results from a Thermofisher Countess II FL Automated Cell Counter. However, the machine we used was not able to differentiate between organisms in a co-culture without fluorescence and, at £4070 (source???), is far more expensive than our DIHM, which cost around £150 to build. Of course, it is often possible to insert a fluorescence gene into a given organism, which would allow for the use of the Automated Cell Counter. Though, this is not always possible and, even when it is, means altering the organisms being studied. Holographic microscopy does not require fluorescence to distinguish organisms and so can be used with wild-type organisms.

There are many techniques that could use fluorescence to calculate the relative densities of organisms in co-cultures. These include, but are not limited to, flow cytometry and fluorescent microscopy. As stated above, our technique does not require that the organisms in a culture fluoresce. This drastically improves the versatility of the technique with respect to the variety of organisms on which it can be performed. Further, we need not dispose of samples after they have passed through the analysis chamber. This means, as was stated with reference to staining and optical microscopy, that there are fewer opportunities for contamination.

This method is cheap, not too time consuming and is non-disruptive - samples need not be taken out of the culture. The idea is that the amounts of products of metabolic processes can be analysed and the growth of each organism that gives a different product can be inferred. For a given pair of organisms, however, it is not likely that their metabolic products are so different that the co-culture could be analysed in this manner. Also, the metabolic rates of organisms can be affected by a great number of variables, meaning that the accuracy of the technique is somewhat limited.

This method is more useful for finding the total cell count of a sample and, even then, it is not renowned for its accuracy, due to the fluctuations in absorbance intrinsic in a biological sample. The absorbance at different wavelengths may be useful for calculating the cell densities of the constituents of a co-culture sample, in the same manner as a pulse-oximeter is used to calculate the ratio of oxygenated to deoxygenated blood in medicine, though this is purely speculation on our part.