Light is pouring into the courtroom. A tense background of hushed conversation fills the room. The defendant, Nosema enters the room. He is a microsporidian parasite. He’s roughly oval shaped and dressed in an orange jumpsuit. He appears infinitesimally small and has a thick cell wall. He stares at the floor, dull and unblinking. Two guards carry him in solemnly. The judge enters.
Bailiff: All rise for the honorable Judge Kara Phyte.
All rise and as the Judge settles in her seat, they follow suit. Judge Kara Phyte is a green alga. She looks composed and just a little bit severe but the water beads forming on her brow betray her. She spent the whole morning photosynthesizing. This is a high profile case. The judge picks up a sheaf of papers, and turns her attention to Nosema.
Judge Phyte: You are charged with murder in the First Degree in the death of Herbert Hostman. How do you plead?
There is a squeak of chairs as Nosema and his attorney rise. The attorney, Perry Mecium helps Nosema up. Perry is a large, hairy ciliate with a kindly air wearing a worn grey suit. His tiny beating cilia brush his client into a standing position. He glances at prosecutor Hugh Glena. Hugh is the very definition of “slick”. Thick protein bands twirl smoothly around the alga’s body, under his plasma membrane. Perry despises mob lawyers like Hugh who defend crooks and put cells who have no voice of their own into prison.
Perry Mecium: Your honor, my client pleads not guilty to the charges.
Judge Phyte: All right, let’s begin.
Hugh Glena: Your honor, I’d like to call our first witness to the stand, Officer Violet Shaw.
A small, velvety purple flower dressed in a green uniform stalks towards the stand and is sworn in.
Hugh Glena: Can you describe what you saw at the scene of the crime, Officer?
Flashback scene. It’s dark and rainy. Violet and her partner are driving in a particularly seedy neighborhood. Red and blue lights are flashing as they hop out of their car and walk towards the crime scene. They see an enormous man reclining on his side, pants half undone in a watery puddle. A spore lies still. A small amoeba advances towards the officers, shaking violently.
Officer Shaw: Yes. Dispatch received an anonymous call at around 1:00 am on the night of the murder. I arrived on scene at about 1:15 am with my partner, Ace. We saw the victim lying in a pool of what looked like his own feces. I also saw the defendant lolling about in the excrement and mumbling something. I brought him into the station for questioning. He didn’t have much to say. He didn’t have to. Microsporidia have been painting the town brown for the last six months but this is the first death we’ve seen in a while.
Hugh Glena: Thank you officer.
Officer Shaw: You’re welcome.
Violet descends from the stand and returns to her seat looking confident.
Hugh Glena: Your honor, our next witness is Dr. Amy B. Proteus.
Judge Phyte nods. A few unicellular spectators rearrange their cytoskeletons to see the amoeba slink along the floor. The bailiff proffers her a tattered lab notebook. The camera focuses on Dr. Proteus and the notebook. We can see the cytoplasm pushing her plasma membrane out forming a pseudopodium that she places gingerly onto the book.
Bailiff: Do you swear to tell the truth, the whole truth and nothing but the truth?
Dr. Proteus: I do.
Hugh approaches the stand.
Hugh Glena: Doctor, you’ve examined my client closely. You’ve delved into the very nucleus of this cell. You know what is in his genome. What can you tell us about the patient? What drives this cell?
Dr. Proteus: I have to say that this is one of the most fascinating cases I’ve seen in years. The most striking thing about the patient is how reduced he is. Ten years ago, we would have diagnosed a patient like this as “extremely primitive”. He has a relatively small genome. It’s so small that it doesn’t encode a lot of the proteins that you and I need to perform many ordinary tasks. He also doesn’t have mitochondria. I’ll remind you that our mitochondria convert food into useable ATP energy and store it. We consume this ATP in a variety of cellular processes. Even his protein making machinery is different from ours. His ribosomes are actually smaller than ordinary eukaryotic ribosomes. In fact, they are the same size as bacterial ribosomes. His remaining organelles, his endoplasmic reticulum and Golgi body are almost beyond recognition. Instead of acting as the protein transport and modfication centers of the cell, they form a unique system of tubules and vacuoles that allow the parasite to invade unsuspecting cells.
Dr. Proteus’ pseudopodia flail as she warms up to the subject of Nosema’s biology.
We used to think that microsporidia like Nosema descended from ancient eukaryotes that lacked mitchondria altogether. We were most excited when we found that microsporidia have organelles that are remnants of mitochondria called mitosomes. We also found mitochondrial DNA in the microsporidian nucleus. So, Nosema’s ancestors had mitochondria just like you and I, but they sort of wasted away over time. These days, microsporidia get their ATP directly from their hosts.
Hugh Glena: So it seems that a cell such as Nosema has a very one-track mind. He’s not much more than a nucleus and infective apparatus in a bag.
Dr. Proteus looks shocked.
Dr. Proteus: Excuse me sir, I wouldn’t go that far but I agree that microsporidia are perfect examples of obligate intracellular parasites that have undergone years of co-evolution with their hosts. Such an organism is completely dependent on its host to complete its life cycle.
Hugh Glena: Thank you Doctor. You can step down. The prosecution calls Dick Tyostelium.
Dick Tyostelium is a cellular slime mold. He’s very ordinary looking amoeba, not too bright. He looks unsettled as the bailiff swears him in.
Hugh Glena: Mr. Tyostelium, You say you saw the defendant at the scene on the night of the murder.
Dick Tyostelium: Yes. I work the night shift at the Agar Bar. I was just on my way home at about 12:30 am when I saw that man collapse. He was HUGE by they way. Then I saw Nosema coming out of that pool of um, you know, poo. I called the police right away.
Hugh Glena: That’s all, Mr. Tyostelium, thank you.
Perry Mecium: I’d like to examine the witness your honor.
Judge Phyte: Go ahead.
Perry Mecium: Mr. Tyostelium, you claim you were coming home from your place of work at around the same time the murder took place.
Dick Tyostelium: Y-y-yes, that’s what I said.
Perry Mecium: Well, I have footage from several security cameras from the Crypto Casino that shows you being escorted away from the craps table. Would you like to tell us again what you were doing on the night of Herbert Hostman’s death? Remember, you are under oath.
Dick squirms in his seat as he watches the security footage. His body is distorted in an expression of terror and he breaks into great convulsing sobs.
Dick Tyostelium: I’m sick. I have a gambling addiction. I was trying to leave it all behind. I borrowed ten grand from Gerry thinking that I would double the lot and pay off my other debts but I lost it all.
Flashback scene. Dick is in an office, bent over in front of a massive desk. He is flanked by two bulky cells and is pleading with the back of an executive chair. One of the hulking cells opens a wall safe behind a picture frame and hands him a wad of money. The scene shifts to the craps table where Dick is being dragged away.
Dick Tyostelium: Gerry told me that if I couldn’t pay the money back, he’d kill my family. I begged for mercy. He told me that he had a score to settle. If I went to this address that he gave me and told the cops that a microsporidia killed a guy, he’d forgive my debts and leave my family alone.
Perry Mecium: Do you mean Gerard ”Gerry” Lamblia, the mafia Don who owns the Crypto Casino? Don’t parasites like him cause giardiasis, a diarrheal disease?
Hugh Glena: Objection your honor, those questions are irrelevant. Mr. Lamblia certainly is capable of causing illness but he has never been convicted of any illegal activities. Moreover, the witness is clearly unfit to give testimony.
Judge Phyte: Objection sustained.
Hugh looks relieved. Perry appears unconcerned.
Perry Mecium: The defense calls coroner, Dr. Penelope Cillium to the stand.
Out from the crowd of spectators, Dr. Cillium, a fungus creeps towards the stand. As she moves, small greenish-grey spheres fall from her head.
Perry Mecium: Dr. Cillium…
Dr. Cillium: Please, call me Penny.
Perry Mecium: Ok, Penny. You performed the autopsy on the victim correct? Can you tell us how the victim died?
Dr. Cillium: Well, first of all, the victim showed signs of dehydration and malnourishment. These symptoms are common in people experiencing microsporidiosis. However, only people who are severely immunocompromised usually die from the disease. I had my lab run a few tests and we found that the victim had a T-cell count well below 100 cells per microliter. The victim, Mr. Hostman was dying from AIDS.
Perry Mecium: Doctor, did you notice any other abnormalities in the victim’s cells? Here’s a micrograph from the autopsy report.
Perry holds up the micrograph in front of the jury, allowing them to examine it carefully. He then places it on a projector for all to see. We can hear a few gasps in the audience. Perry continues. The image shows neat, tiny holes in the plasma membranes of a few intestinal cells.
Perry Mecium: How would you interpret these wounds Dr. Cillium?
Dr. Cillium: Well, the approximate shape of the wound corresponds to a sharp, thin, tubular object. The dimensions of the defendant’s polar filament roughly match the size of the entry wound.
The camera pans over to Hugh Glena. He looks pleased.
You see, the polar filament is a sort of coiled tube that shoots out of the microsporidian spore and penetrates the host cell. Immediately, the contents of the spore are fed into the host cell through the filament. Multiple rounds of cell division occur and many new microsporidia break out of the victim’s cell and spread. The only way Nosema could have gotten out of those cells is by bursting out. A handful of microsporidian infections have crossed my table and the cells rupture completely after infection.
Dr. Cillium demonstrates an exploding cell by waving her hyphae, the slim, graceful threads that make up her fungal body then stops suddenly. She has just realized that she made a grave error in her examinations.
Perry Mecium: So, the cells should not have remained intact if Nosema had infected them, correct?
Dr. Cillium: Yes. I never thought about that since Nosema was found on the scene. We usually just diagnose microsporidiosis when we find microsporidia in the victim’s stools.
Perry Mecium: So you’re saying it’s possible that some other pathogen could have caused Mr. Hostman’s demise?
Dr. Cillium: Yes, it’s possible.
Perry Mecium: That’s all Dr. Cillium, thank you.
The courtroom breaks out in discussion in light of this new evidence. Judge Phyte hammers her gavel.
Judge Phyte: Order in the court! Order!
The room gradually falls silent.
Perry Mecium: I have no further questions your honor.
Judge Phyte: Well, I think we have heard all the arguments. I’d like to hear any closing statements.
The camera pans over to Hugh Glena. Hugh is stunned.
Hugh Glena: The prosecution has nothing more to say.
Perry Mecium: I would like to make a closing statement your honor.
The judge nods and gestures towards the jury.
Judge Phyte: Go ahead.
Perry begins pacing in front of the jury box. One by one, he makes eye contact with each of the jurors. Some of them try to avoid his piercing looks.
Perry Mecium: Members of the jury, when you leave this courtroom you will be deciding the fate of a cell. I need you to put your prejudices aside. Imagine yourselves in Nosema’s cell wall. All your life, other organisms have looked down on you or even feared you because you’re a parasite. Even other fungi, your own closest relatives can’t stand the sight of you. It’s not your fault. You don’t choose to depend on others for your survival, things just ended up that way. If that isn’t bad enough, your host has died and you’re out there in a fetid box of kitty litter. The next thing you know, you’re lying in a pool of human waste next to a dead man and you have no recollection of being in a mouth or even passing through an intestinal tract. You want to explain the situation to the police but you can’t because you haven’t got the energy, you’re in your resting state.
Perry pauses for a moment. His cilia beat rapidly as he delivers his passionate address.
Now, if you can say without a shadow of a doubt that Nosema is the killer, I urge you to follow your inclinations. However, if you have even the slightest doubt, you need to do the right thing. After all, it is better that ten guilty cells escape rather than let one innocent suffer.
Judge Phyte: Court is adjourned until 3pm when the jury will give us their decision.
The jury shuffles wordlessly out of the courtroom. At 3pm, they return. The jury chair rises.
Jury Chair: Your honor, we find the defendant not guilty.
Hugh Glena slaps his flagellum on the desk in anger. The scene skips to the outside of the courthouse. Reporters are jostling about trying to get a statement from Perry Mecium and Nosema. Suddenly, a gunshot rings out. Nosema collapses onto the ground just as he was about to duck into a car. The stunned crowd looks around to find the assailant. A shiny black town car stops behind a local news van. We catch a glimpse of Gerard Lamblia in the back window. He wears dark sunglasses but a smug look steadily creeps across his face. The window rolls up smoothly and the car drives away.
Keeling, P.J. and N.M. Fast. Microsporidia: Biology and Evolution of Highly Reduced Intracellular Parasites. Annu. Rev. Microbiol. 56:93-116. 2002.
Keeling, P.J. and C. H. Slamovits. Simplicity and Complexity of Microsporidian Genomes. Eukaryotic Cell. 3(6): 1363-1369. 2004.