The riddle of the 'green streaks'

In search of the first microorganism which Antoni van Leeuwenhoek described.

by Wim van Egmond, the Netherlands
in collaboration with Frans Kouwets

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During the summer of 1674 Antoni van Leeuwenhoek (1632-1723), a draper from Delft, filled a small bottle with water from a lake called the Berkelse Meer. He examined the contents with his microscope the next day. His description of the find and what he observed using his tiny but superb microscope can be regarded as the beginning of microbiology. He wrote about this discovery in Dutch. His letter, dated September 7th, was sent to the Royal Society in London, translated into English and an extract published in Philosophical Transactions. Although the language in which he wrote is a bit old-fashioned it is still a treat to read. Here is the English translation. (The original letter was one long paragraph, I split it into 3 parts for easier reading.)

Portrait of Van Leeuwenhoek by
Johannes Verkolje.

There has always been a lot of speculation about the true nature of the organisms he described in this letter. Van Leeuwenhoek was a layman and it was long before Linnaeus provided us with a systematic way of describing living organisms. Almost everything Van Leeuwenhoek observed through his simple single lens microscope had never been seen before. Van Leeuwenhoek did not give the organisms names, he simply described their appearance, as detailed as he could.

He was one of the best observers of his time. In any case literally because he was the only one who could make a microscope with a magnification of up to several hundred times and with a very high resolving power.

Spirogyra photographed in darkfield illumination. Image width: approximately 0,9 mm.

In 2009 our Dutch desmid club (www.desmids.nl) organised an excursion to the Czech Republic to collect some samples of this group of beautifully shaped green algae. During a field trip I was talking with Frans Kouwets, phycologist at the Ministry of Infrastructure and Environment in Lelystad. Somewhere during our conversation I mentioned Spirogyra as the organism found by Antoni van Leeuwenhoek. 'Aha', Frans said, 'that is something that I seriously doubt. I don't think it was Spirogyra and perhaps it is interesting to publish something about this.'

It is now 2016 and Frans and I have discussed this subject over the years. I have studied Van Leeuwenhoek for my work for a museum about microbes, continuously finding new clues. An extra reason why I am so interested is the fact that I grew up near the location and live near the former Berkelse Meer. Frans currently is very busy with his monograph of the desmid genus Cosmarium and encouraged me to write the article. But Frans is reading over my shoulder so don't forget that he started all this.

Let's start to sum up the reasons why we think Spirogyra is an unlikely candidate. And perhaps it is a good moment to refer to the motto of the Royal Society; Nullius in verba, which can be translated as 'take nobody's word for it'.

Spirogyra is common in shallow ponds and ditches. A large lake as the Berkelse Meer was (1.5 kilometer wide) is not the usual habitat. Although it inhabits lake edges it is not planktonic.

Spirogyra does form floating masses but in early summer, and then their color is not whitish green but yellow or brown green.

Spirogyra blooms consist of very long filaments or strands, not microscopic streaks.

Being such a keen observer, Van Leeuwenhoek was always very accurate in his observations. He would certainly have described Spirogyra as long strands. If you find Spirogyra you can take it out of the water with your hands as scum, and it feels slippery.

Van Leeuwenhoek used capillary tubes at the time for studying liquids e.g. in his earlier letter dated July 6th 1674. If he did it would be impossible to put Spirogyra in such a tube. 

There is enough reason for doubting it was Spirogyra. It is interesting to see that for such a long time everybody copied Dobell's suggestion, although it is understandable. What else could it have been? Before we search for other candidates, let's look again at the description.

"I found floating therein divers earthy particles, and some green streaks, spirally wound serpent-wise, and orderly arranged, after the manner of the copper or tin worms, which distillers use to cool their liquors as they distil over. The whole circumference of each of these streaks was about the thickness of a hair of one's head. Other particles had but the beginning of the foresaid streak; but all consisted of very small green globules joined together : and there were very many small green globules as well."

and the original letter in Dutch: 

"bevonde ick daer in te drijven, verscheijde aertsche deeltgens, ende eenige groene ranckjens, in geschickte ordre slanghs gewijse omgekrult, op gelijcke manier, als de copere off tinne slangen sijn, die de distelatuers gebruijcken, omme haer over gehaelde wateren te verkoelen, ende de gantsche circumferentie, van jder van dese ranckjens, hadt ontrent de dickte van een haer van ons hooft; andere deeltgens hadden maer een begin, van het boven verhaelde ranckje, alle bestaende uijt seer kleijne groene same gevoeghde clootgens, als mede seer veel kleijne groene clootgens,"

Van Leeuwenhoek only wrote in Dutch. He did not know any other language and his Dutch is translated by others. That is why I think we should look at the original Dutch text and try to read it as carefully as possible. The actual Dutch word Van Leeuwenhoek used was 'ranckje' (plural ranckjens). While writing this article I noticed that the English translation of the word 'ranckjes' (both in the Collected Letter's and Dobell's), into 'streaks' is not accurate. The word streak is a bit misleading because it suggests an elongated shape. In my opinion a correct translation would be small tendril. And I am sure he used the Dutch equivalent because a tendril is often coiled. The Dutch text is even clearer on the coils than the translation.

It can be translated various ways. Here's what I would make of it: Several earthy particles and some green tendrils that are bent snake-wise to orderly arranged curls, like the copper or tin tubes distillers use to cool their transferred water.

A distiller's copper worm.

Van Leeuwenhoek literally describes his find as regularly ordered coils made out of little balls (clootgens). Resembling a vine tendril and a distiller's copper worm (shown above). Many of his descriptions are cryptic and hard to associate with certain organisms. That is true for the other organisms he describes in the latter part of the letter. But this section, the first time aquatic microbes are ever described, is clear and accurate. We also have the details of the time and setting. In his boat on the Berkelse Meer, a nutrient rich lake (plenty of fish) Antoni van Leeuwenhoek describes a late summer cyanobacterial bloom and the first aquatic microbe captured in words could very well be the one shown here:

 

The image shows what Frans and I suggest to be the most likely candidate. It's a filament-forming cyanobacterium. They are made out of little balls, the individual cells, that form very regularly coiled strands. I found these myself in late summer in a large lake as a whitish green layer against the surface. During August there was a bloom of these cyanobacteria. So the time and location also fits the description. I have collected them the same way Van Leeuwenhoek did. They float under the surface as a cloudy layer and when you put a bottle in the water you can easily fill it.

Cyanobacteria, or blue green algae, are bacteria that perform photosynthesis. Although they have a bad reputation they are important oxygen producers. The cyanobacterium that we think Van Leeuwenhoek described is in the genus Dolichospermum. Recently the planktic forms of Anabaena were separated from this genus and transferred to the genus Dolichospermum. The coils of this species of Dolichospermum have a diameter that range between 70 and 90 microns. Van Leeuwenhoek is talking about the whole circumference (not the little cells) measuring about the same as the thickness of a hair from our head. According to the DNBL Collected Letters website the size of such a hair is between 60 and 80 microns.

Dobell ruled out the helical cyanobacteria Arthrospira and Spirulina and I think he was right. Their filaments are more slender but more importantly, they are not made out of little balls.

Frans and I can't think of any other suitable candidate. If we compare all the arguments in favor of Dolichospermum and all the arguments against Spirogyra there is only one conclusion. It is much more likely that Van Leeuwenhoek observed cyanobacteria like Dolichospermum. And that would mean it is not only the first account of living aquatic microorganisms, but also the first observation of bacteria, two years before Van Leeuwenhoek described them in his studies of 'pepper water' in the letter dated October 9th 1676. 

I think it is important to state that we can only speculate here. We can't be 100% sure. But in the case of the greenish helix of little balls we can safely replace Spirogyra by Dolichospermum, the cyanobacterium formerly known as Anabaena, as the number one candidate of the first described aquatic microorganism.

Microcystis

Footnotes
There are many different species of Dolichospermum with various dimensions that form coiled filaments so it could well be that Van Leeuwenhoek saw a different species. But there are not that many species with a regular coil of the diameter Van Leeuwenhoek mentions. If we follow the description of a regular coil with the diameter between 60 and 80 micron we can narrow it down to D. circinale, D. spiroides or D. crassum. The one I photographed may be D. crassum but not without doubt because these species vary in appearance and are hard to distinguish from one another.

A paper by Jirí Komárek and Eliška Zapomelová published in Fottea (Journal of the Czech Phycological Society), 2007, vol. 7, issue 1, 1-31, presents a detailed and richly illustrated review of these coiled cyanobacteria. Planktic morphospecies of the cyanobacterial genus Anabaena = subg. Dolichospermum – 1. part: coiled types. 

Acknowledgements
This article was written in collaboration. I would like to thank Frans Kouwets for allowing me to publish this investigation that started with his initial idea and for the feedback during the writing of this article.

Micscape’s editor David Walker was a great help and offered valuable suggestions. Read his article 'Reflections on studying Spirogyra' which includes images of a Spirogyra species taken using a commercial replica of a Van Leeuwenhoek microscope.

I also would like to thank Richard Howey and Maria van Herk for their feedback and help.

Thank you to the Digitale Bibliotheek voor de Nederlandse Letteren (DBNL) website for both hosting and making freely accessible the first fifteen volumes of the 'Collected Letters of Antoni van Leeuwenhoek'.

Image credits
All material (except the maps, tendril, copper tin image and images as described below) © Wim van Egmond.
The portrait by Johannes Verkolje of Antony van Leeuwenhoek F.R.S. from the frontispiece of Hoole's 'The Select Works of Antony van Leeuwenhoek', published in two vols. ca. 1800. Now in the public domain at www.archive.org.
Van Leeuwenhoek diagram from Plate XXXI of Clifford Dobell's 'Antony van Leeuwenhoek and his "Little Animals"' in the public domain at www.archive.org.
The Berkelse Meres Map is an enhanced detail from: 't Hooge heemraedschap van Delflant / Nicolaes en Jacob Kruikius (1712). Source: Hoogheemraadschap van Delfland te Delft inv.nr. OAS 726 from the Delft University of Technology website with thanks.
The distiller's copper worm image is web sourced but exact credit uncertain, but will be pleased to add due credit if contacted.

Revision history.
First published February 13th 2016.
Various minor revisions up to and including February 16th 2016.