Bowen Jiang

Bowen Jiang

Nov 18, 2017

Group 6 Copy 2,222
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Algae at high school??

Yes, I am indeed this much of a nerd. But that's not really the point here.

So, high school. Instant thoughts: "...musical", "ugh calculus", "pre-adult freedom" (enjoy it while you can). Yet have you ever considered the quintessential abode of secondary education to be prime algal habitat as well? Of course not. (Somehow I predicted that.) That's cool. But now that the first appreciable rains have come to Sacramento and native plant life can once again attempt to grow, I thought it would be pretty appropriate (and who knows, maybe even interesting) to look at some of the itty-bitty microscopic plants that have decided to pick here and now as their growing season so that you, too, can have the knowledge of high school algae. Don't question it. Just roll with it.

But wait. Algae at a high school??? you might be thinking. Does your school have its own lake? If it rains anymore, one might think it could happen. But no, it does not.

Then what's the deal?

I believe I may have mentioned it in passing in an earlier lab note, but not all algae grow directly immersed in large permanent bodies of water, like the archetypal marine seaweeds or freshwater pond scum one might think of after hearing the word "algae". A good number of them can grow directly on rocks and concrete, like mosses; others live in dirt; many species reproduce quickly enough to survive in short-lived bodies of water like puddles; and some really wacky ones live directly in the air, survive encased in snow or ice, grow in layers of dust in the desert or even within other organisms! As long as water is available in some form, there's always the potential for algae too. Mira Loma High School is not a particularly extreme environment in this sense, so the algae in question I've seen around campus mainly belong to the first three ecological categories. Two species are very common and visible year-round on some concrete surfaces, another three are ubiquitous soil species, and at least four more (and some small animals and protists) can only be found in puddles after large rains; however, all three ecological types require the rain to grow their best. I haven't catalogued all of the algae in every possible environment across the school, but there are around 8 that are very easy to find and that I've seen frequently, which I'll share here.

So let's get started, habitat by habitat!


Concrete and Pavement

Green algae growing around a gutter outflow.

Scientists still aren't exactly sure how the plants proper evolved; DNA evidence has helped us find their closest algal relatives, but we're still working on understanding the process by which they colonized land. Algae like the ones pictured above, which are still relatively simple but that have managed to grow in terrestrial environments, may be the key to uncovering the secrets of this transition. As long as they get soaked in water every now and then, species such as these can survive on wood, stone, cement and concrete, even through the Californian dry seasons.

Here is a small piece of the alga Klebsormidium, collected from the above area and magnified at 400x:

A small chain of Klebsormidium. Note the small semicircular chloroplasts stuck to the bottom of the cell walls of the rightmost cells (arrows). 

Klebsormidium is one of the most common genera of terrestrial green algae, and I do have one strain of it currrently in culture (JIAC23). They often grow with moss or by themselves near gutters or drains, which may flood periodically and soak them in enough water to keep them growing for a few days before they dry out again.

The dominant alga I found on the pavement, however, was a different species, which looks like this:

Chloroidium sp.?

It grows mostly as these small cocci (spherical cells) which occasionally clump together. Unfortunately, it is very difficult to find any identifying characteristics, as it is pretty much just a little green ball (a legitimate and cited term!). It is for relatively understudied algae such as this - terrestrial and almost impossible to classify with only a regular light microscope - that DNA analysis holds the greatest potential for improving taxonomy. As I had previously collected a very similar alga from a sample of wood within the vicinity of the school and sequenced that alga's DNA, I am going to guess this is a species of Chloroidium, a lineage of trebouxiophytes that is well known (in fact, almost defined) by terrestrial growth. However, the taxonomy of this genus is still uncertain, and the studies that have tried to tackle it are relatively young.


Soil Algae

As the name implies, soil algae are those that can live in soils, where the ambient moisture is great enough (most of the time) for them to actively grow and reproduce year-round. Of course, in California, that isn't always the case. In my experience, finding algae directly in the soil isn't impossible (I cultured some from lawn clippings way back when I was in elementary school), but often it takes a lot of time and luck and risks creating a death-cloud of mold spores, which nobody really wants. So, as with the last group of algae I'll discuss below, I most often encounter soil algae growing at their absolute happiest and in greatest numbers after heavy rains, when water can collect and release them from the confines of the dirt.

One of the most famous soil algae is Chlamydomonas reinhardtii, a single-celled species closely related to the colonial globe algae genera in the order Volvocales (also known as Chlamydomonadales). A variety of factors have contributed to it becoming a model organism in the lab (sort of like what the thale cress Arabidopsis thaliana is for plant studies, or the lab rat for animal studies), where it has been used for the study of hydrogen production, starch synthesis, biofuel prospecting, genetic engineering, photosynthesis, multicellularity and more. Here is a labeled image of one cell, photographed at 400x:

An archetypal cell of Chlamydomonas, with major features labeled.

The whole round ball is the cell, but unlike those of Chloridium, the cells of Chlamydomonas have lots of easily-identifiable features. First, note the chloroplast (not labeled); it is the entire green area within the cell and is shaped like a "U" or a cup. The upper center region of the cell is clearer and non-pigmented; at the very top of the cell is a small round organelle, the contractile vacuole. This organelle inflates and deflates every 10-20 seconds or so, pumping water out of the cell that tries to flood in due to osmosis. (Cells prefer to have water flow into the cell, known as a "positive water balance", because it is easier to push water out of the cell than it is to try and take it in or retain it in the cell.) Sticking out of the top of the cell are two faint flagella, small protein filaments which the cell can whip around to create a current and move itself. The cell often likes to swim towards light so it can photosynthesize, and it detects light using an eyespot, the tiny red dot in the cell. The last organelle, the pyrenoid, is used for photosynthesis. It is a very large organelle, bulging out of the chloroplast (sometimes appearing to take up a third or a half of the cell's profile), and it concentrates carbon dioxide collected by the cell to make photosynthesis, and specifically the process of transforming carbon into sugars, more efficient.

In addition to Chlamydomonas reinhardtii, I've found some other unidentified unicellular species which I suspect are also normal soil algae of the family Volvocales:

Miscellaneous algae. Large colony to the right is Pandorina; small spheres are Chlamydomonas; arrows are other unidentified species.

These have many of the same anatomical features that Chlamydomonas do, such as an eyespot, two anterior flagella and pyrenoids, but they are differently shaped and sized. One of these (towards the bottom) is almost square in shape, whereas the other one is more oval. Both of these are smaller than the average mature cell of Chlamydomonas, and they tend to swim faster as well. I'm currently working on culturing algae from this sample, but I haven't been able to find any pure cultures of these smaller species. Hopefully I can get one, because I feel like they would be a lot of fun to study. The Chlamydomonas for sure will be extremely useful for many of my future projects, which I still plan to cover in a future lab note soon.


Muddy Puddles and Other Ephemeral Waters

Streetside puddle. Notice how it's formed over gravel and dirt, not flat pavement; the dirt holds both algal "seeds" as well as key nutrients they need to grow and reproduce.

Finally, I arrive at the reason why I wanted to write this whole lab note (although on second thought, it should probably be a field note. More on that in a future post). Now that the rains have returned, large puddles form on one of the main streets that leads to the school, and they collect in areas also filled with lots of dirt. The puddles typically remain for at least a week or two - sometimes months - before drying out, assuming they're filled with appreciable rain, and during this time an entire host of algal species arise. The soil algae, as I mentioned above, take this opportunity to make themselves visible; however, many other species can only survive fully immersed in water, so the puddle's lifespan directly affects theirs. In the summer months, they remain dormant in aplanospores, small diapausing cells that can survive in dry environments but do not actively grow (like brine shrimp), but as a temporary or ephemeral body of water forms and nutrients from the dirt leech into the water, the algae can form large blooms that will even turn entire puddles a bright green color in optimum conditions. Eventually, the puddle dries up, the algae form new aplanospores, and the dry season sets in again.

The best well-known of these ephemeral algae belong to the order Volvocales. While some (such as certain species of Chlamydomonas and the red Haematococcus) are unicellular, the most impressive are colonial, multicellular species which have the common name of "globe algae" (athough this typically refers mostly to Volvox, I think it is appropriate for all of the colonial Volvocales). In this puddle, three genera predominate: Eudorina, Pandorina, and Gonium.

Eudorina, which I started a culture of last year and plan to restart this year, looks like this at 400x:

A 32-celled colony of Eudorina.

The colony is oval-shaped overall, consisting of either 16 or 32 (powers of 2) cells embedded within a clear sugary gel, known as a polysaccharide extracellular matrix, which form the faint outline around the cells. Notice how the cells, by and large, appear very much like those of Chlamydomonas: eyespots and flagella (2 per cell) are notated here, and the cells also have pyrenoids and contractile vacuoles. However, as the colony is multicellular, the cells coordinate their motion and light sensing abilities to constantly swim towards light and rotate in place, maximizing the photosynthesis time for each cell. In fact, Eudorina swims quite rapidly (visible to the naked eye) and within about 5 minutes of placing a light on one end of a jar, almost all of the colonies will swim towards that one end of the jar, forming long "columns" along its edge to maximize the number of cells that can stay in the area of greatest light intensity.

Pandorina is very much like Eudorina, except its cells are larger, wedge-shaped, and packed closer together:

A colony of Pandorina. Note the "orange-slice" shape of the cells; while that alone isn't a diagnostic characteristic, many species and strains of this genus have closely compacted cells.

Again, however, its cellular components are practically the same as that of Chlamydomonas.

Finally, there is Gonium, which unlike the previous two genera is pretty much always 16-celled (in mature, healthy specimens) and flat in colony shape:

Gonium at 400x. Note that eyespots are present in each cell; they just do not appear in this line of focus.

And yet again, its individual cells have identical anatomies to Chlamydomonas.

Why is this relevant? Again, Chlamydomonas and these three genera of algae all belong to the order Volvocales, which also contains the larger and more famous Volvox. It is commonly assumed that Chlamydomonas represents an evolutionarily older ancestor, from which these algae gradually developed more complex and larger colonies over time, succeeding each other in degrees of "advancedness" based off of these two factors, colony size and cell number. However, Japanese researchers, who have performed the bulk of study of this order of algae, have determined that it's not this simple - multicellularity evolved multiple times in the Volvocales (meaning that several single-celled ancestors formed larger colonial species, and the evolution of colonies is not a singular, linear process). In addition, lots of work in this order of algae has shown that the species Chlamydomonas reinhardtii consists of many many different strains, some of which were first isolated and identified decades ago, which are not all related and not all truly Chlamydomonas at all. So beyond the simple aesthetic and entertainment factor that the globe algae definitely have, these could be useful in future taxonomic and phylogenetic studies of the Volvocales, so I'm working on culturing as many strains from these samples while the rains last so that I can photograph them, make visual observations, exact and preserve DNA samples, sequence some major genes, and eventually send them off to be permanently stored in larger culture collections where they will be continuously maintained and can later be used for any subsequent algal study.

Alright, so in case you were ever curious about algae that live on land, in temporary bodies of water, or at school...that's the very long, very roundabout answer. In my next post, I will be sure to discuss future project ideas and continuations, provide another update on the current progress of the project, and inform you about a new algal blog I'm going to create. Stay tuned.

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About This Project

The aim of this research is to find and test gene regions in the genome of freshwater green algae which can aid the identification of species in this taxon. These so-called molecular barcodes will be amplified by PCR and compared by sequence analysis, and their successful application will aid greatly in determining the current taxonomy of green algae, as well as conducting environmental surveys, identifying new species, or selecting strains for potential human use and applications.

Blast off!

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