Marine Bacteria Encapsulation--Success!

After months of work and lots failures and successes, my encapsulation technique for marine bacteria finally worked! As mentioned in a previous post, I have been volunteering at the Bradley S. Moore Lab at the Scripps Institution of Oceanography since April 2018. After summer break, I began an independent project that I am still working on and will continue to explore throughout my senior year of college. In short, the lab's overall goal is to discover natural products from bacteria in the sea. Some of these bacteria reside in sponges, but their ability to grow in three-dimensional animals like the sponge makes it difficult to grow them on the flat surfaces or in liquid solutions we traditionally use to grow bacteria in lab.

Because we need to be able to grow bacteria to find and use the chemicals they produce for medicinal purposes, I have been working on a new technique for growing space-dependent bacteria in the laboratory. This technique includes encapsulating bacteria in micro-orbs made of a sugar and chitosan. Encapsulation can be compared to putting bacteria into a jelly-like substance and enclosing the "jelly" in a casing. In the past, I was successful in growing terrestrial bacteria with this technique, but ran into problems when I switched to growing marine bacteria.

Capsules under a microscope.

The issue with the capsules with marine bacteria and in seawater depended on a few things. First, I noticed the marine bacteria were dying once encapsulated. After a bit of thinking and trial-and-error, my mentor and I found that this was because the pH (or acidity) of the sugar I was using was too low. The pH of the ocean is about 8. The acidic nature of the sugar was killing the marine bacteria before they could even be encapsulated in chitosan. 

Second, marine bacteria are used to surviving in salty seawater, and the sugar did not contain salt. The osmotic imbalance of the cells and the sugar may have been popping the cells. We were able to adjust the balance of salt in the sugar mixture to match the balance of different salts commonly found in the ocean to make sure the bacteria were happy, healthy, and staying alive during encapsulation.

Known marine bacterial species, Shewanella japonica, is grown using encapsulation and popped on a plate for visual confirmation of the technique's validity.

Once we were able to make the proper pH and salt adjustments, marine bacteria were able to be encapsulated, grown, and cultured like the original terrestrial species! 

Now, I am experimenting with using the capsules to separate a mixture of many types of bacteria. Stay tuned for more updates to come!

                                                    -Em