A brief history of the techniques used to look at seaweed-bacteria interactions in the last 100 years

Macroalgae are known to have a very diverse range of bacteria associated with them, whether they are epiphytes, or those which live within the tissues of the algae. This is because seaweed surfaces provide a hotspot for bacteria, and the attraction of these bacteria to the seaweeds is highly specific due to the physiological and biochemical properties of the host. They may be beneficial (mutualistic), harmful (parasitic), or have no effect on the algae. This wide range of where the bacteria are present in/on the algae, combined with the applied aspects makes seaweed-bacteria interactions appealing for ecological, evolutionary and biochemical studies. This paper is a review on the progression of observation of seaweed-bacterial interactions and associations over the last 120 years, and how these interactions may be of use to us.

In 1881, a German Physician, Walther Hesse joined Robert Koch’s laboratory in order to identify the bacteria which were making his patients ill. However, the gelatin-based culture medium he was using liquefied due to the bacterial enzymes or incubation temperatures. He then went home and told his wife about the conundrum, to which she suggested he use a seaweed extract, agar-agar, which she used to thicken her jellies and puddings. This initial discovery is what began the acceleration of bacterial research. Bernard Fischer (1889) used this technique, and noted that the greatest culturable marine bacterial abundance was associated with planktonic organisms and seaweeds. Marine bacterial abundance was observed to be greatly associated with seaweeds in the Atlantic and Antarctic Oceans by Hans Gazert (1906) too. In fact, these were some of the largest bacterial populations found in the vicinity of seaweeds. This was also confirmed by another team of scientists at a laboratory doing similar work at the same time. It was the presence of epiphytic Azotobacter on marine algae which lead Johannes Reinke (1903) to suggest a symbiotic relationship. Also, Director of our own Marine Biological Association of the UK, Edgar Johnson Allen (1910) and his collaborator, E. W. Nelson also recognized symbiosis in xenic macroalgal cultures.

It was after World War 2 that cultivation and microscopy studies took place, beginning with Luigi Provasoli & co. being the first to establish bacteria-free cultures of Ulva spp. Using new antibiotics. In the 1970’s, electron microscopy enabled scientists to discover intracellular bacteria as well as epiphytic bacteria in various siphonous seaweeds. Some of these bacteria appeared to be host-specific, with obvious differences between the Cholorophytes, Rhodophytes and Phaeophytes. A stable association between the algal hosts and bacteria were observed even though the bacteria may vary throughout and between the seasons, and different parts on the seaweed.

Bacteria are vital to the health and productivity of macroalgae, which also has a detrimental effect on us. We use macroalgae in a variety of ways, for example food products, cosmetics, biomedical usage, and many everyday items. If there is an upset in balance of bacteria-algae interactions, there could potentially be a large economic loss. For example, algal bioactive compounds have antimicrobial properties to protect its surface from undesirable microorganisms. These could be used in biomedical research or in industry, such as anti fouling paints.

I enjoyed this review because it is interesting to see how our techniques have developed over the last 100 years or so to reach the point we are at now. I enjoy learning about early techniques and how they came about, so I found this review a nice read.

If any of you are interested, here is the review reference:

Hollants, J., Leliaert, F., De Clerck, O. & Williems, A. (2012) What we can learn from sushi: a review on seaweed-bacterial associations. FEMS. 81(1): 1-16.

Or here’s the link:

http://users.ugent.be/~fleliaer/publications/2012_Hollants_FEMS.pdf