Carolyn’s lecture today focused on examples of different pathogen groups. The first group we looked at was fungi, using Abalone Shell Mycosis as a study case. Marine fungi tend to be rare or unnoticed, so a marine fungal disease is quite interesting. The disease had a large impact on New Zealand, where it impacted important Pāua (abalone) species such as Haliotis australis, H. virginea, and H. iris. Because of the sand-like mineral deposits that form in the lesions caused by the fungi, it was originally believed that the disease lesions were actually physical damage from sand. However, histological analyses (among others) revealed fungal hyphae in the lesion, implicating a fungus identified as from the class Deuteromycotina. Another disease-causing marine fungus is Asperigillus sydowii of the sea fan Gorgonia ventalina.
The next group looked at diseases caused by metazoans. I really loved this section – the pathogen was a sabellid polychaete (annelid worm) in abalone. The polychaete was brought into California from South Africa via imported Haliotis midae and spread by the aquaculture industry. It’s a really neat pathogen, forming mucus tubes along the leading edge of the abalone shell, which the host then covers up with its own shell. This causes abnormal growth of the shell and weakens it – making for very sad abalone. Even though it spread into the marine environment through aquaculture outflow, it was apparently eradicated in natural populations by culling gastropods – it was an incredible success story. Neat fact: the worm is a simultaneous and self-fertilizing hermaphrodite, meaning that it only takes one to start an infection!
The last group we looked at was bacteria, specifically Nocardia crassostreae and Vibrio harveyi. Nocardiosis affects Pacific Oysters (Crassostrea gigas) in which they are implicated with summer mortality on the West Coast but not in Japan. Vibrio harveyi presents great case of the disease triangle in European abalone (Haliotis tuberculata). The disease is temperature sensitive with a change of 1ºC eliciting a large increase in mortality. The disease also depends on the host, which is more susceptible while spawning. Lastly, Vibrio harveyi isn’t homogenous in itself – depending on the presence of a plasmid, the bacterium may or may not be virulent.
For lab, we started our experiment looking at the possibility of using oysters as a biocontrol of eelgrass laby. Oysters potentially could filter out laby from the water column and make them less likely to infect eelgrass. We had four groups in our experiment in triplicate, each having a total volume of 225 mL in a 250 mL beaker. Two of the groups had oysters (10 per beaker) as treatment groups, and the other two had none. Two also had laby in them (at a currently unknown concentration due to the difficulty of getting concentrated cultures). All of them were treated with pen+strep to limit other growth and had a spin bar to maintain gas exchange. Our set up was as follows:
|Oysters||Ultimate treatment!||Better have no laby at all…|
|Control (none)||Should give us a Laby baseline||There should be nothing happening here at all…|
From each beaker we’re taking 1000 μL water samples to quantify the amount of laby in each of them at 0, 1, 2, 4, 8, and 24 hours. After the completion of this portion of the experiment, we’ll be putting in eelgrass shoots to see if we can get infection! What we might hope to see is that the treatment with the oyster will have less (or no) infection as compared to the laby only treatment. We’ll also be dissecting the oysters and blotting some of their tissue onto plates to see if we can get viable laby.
We also looked at the gels that Allison and Lauren ran using the same DNA extracts and PCR primers as we did two (?) days ago. For the most part our results were the same, easing our minds that any issues we saw were not from operator error and cluing us in that problems were probably with the primers themselves. The WC primers for laby performed quite nicely again, producing the same bright bands as before. It was a nice confirmation that I didn’t mess up my first PCR O.O