BIOBROKERS AS CATALYSTS AND AS GATEKEEPERS

BIOBROKERS AS CATALYSTS AND AS GATEKEEPERS

Post # 20

Donald A. Windsor

An interaction between a parasite and a host is like a chemical reaction.

Parasite + Host ==> ParasiteHost complex P + H ==> PH

A biobroker acts as a catalyst. P + H == biobroker ==> PH

This analogy helps me to understand my basic amazement at the complexities of biology. Nature seems to be a giant nexus of multiple species so tightly bound together that it resembles sticky cotton candy on a hot humid day.

Consequently, I visualize interactions between two species as involving multiple species. Species interactions are not between species, but among species. Many of these interactions have participants that operate behind the scenes.

Some of the behind the scenes mechanisms of biobrokers are especially interesting. A recent article reports that Bacteroides fragilis attaches itself to the gut epithelium of mice by adhering to the mouse’s immunoglobulin A. The bacterium then rules by excluding invasive pathogenic microbes (1). It acts as a gatekeeper, or in my view, a biobroker. The presence or absence of this bacterial species determines whether or not a pathogenic bacterial species (a parasite) can or cannot infect this mouse and use it as a host. The host species has retained Bacteroides fragilis to exclude parasites and to allow commensals.

                                       / ==> P + H Interaction prohibited; parasite excluded.

C + P + H == biobroker

                                       \ ==> CH Interaction accepted; commensal allowed.

To infect this host a parasite would have to overcome the biobroker.

P + H === biobroker ===> PH Interaction overcame biobroker.

In metazoan parasites and hosts this biobroker role could be played by competitive parasites.

References cited:

1. Donaldson, G.P. ; et al Gut microbiota utilize immunoglobulin A for mucosal colonization. Science 2018 May 18; 360(6390): 795-800.

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INTERMEDIATE HOSTS AND BIOBROKERS -- DEER BRAINWORM

INTERMEDIATE HOSTS AND BIOBROKERS − DEER BRAINWORM

Post # 19

Donald A. Windsor

Having intermediate hosts in a parasite’s life cycle must confer some survival advantage. But what? Some parasites have them; some do not, and some have two. Having or not having intermediate hosts seems to depend on particular situations. This subject has been well covered. It was even modeled (1). A recent review was published in 2015 (2).

My interest is in the participation of other species in the parasite-host interactions, the biobrokers (3). Life is more complicated than we realize and species interactions seem to involve more than merely two species. The other species are not readily seen.

A good example is the deer brainworm Parelaphostrongylus tenuis. This nematode has the white-tailed deer (Odocoileus virginianus) as its definitive host and several species of snails and slugs as its intermediate hosts. Worm eggs hatch in the deer’s bloodstream and the larvae travel to the lungs, get coughed out, swallowed, and defecated onto the ground vegetation. Snails and slugs (gastropods) eat the mucus coating on the scat pellets which contain the larvae. When the deer graze they inadvertently ingest the gastropods. The larvae from the gastropods travel from the deer’s gut to the central nervous system, where they mature, breed, and lay eggs in the blood stream (4).

The biobrokers in this interaction between the deer and the gastropods are the many species of ground vegetation. These plants have to be palatable, or at least not repulsive, both to the deer and to the gastropods. The point is that other species are involved in the interaction between the deer and the gastropods. The biobrokers would not be needed in a lab setting, but my concern is what happens in nature. The participation of the gastropod intermediate hosts offers an additional conjecture.

The brainworm is further involved in a complex network of other host species besides the white-tailed deer. In moose (Alces alces) it is usually fatal, unlike in deer where it usually is not. Consequently, overlap of these species is inhibited.

It could be argued that a biobroker is no different from a non-biological thing. Indeed. I frequently confront that thought. Inert, synthetic Astroturf could be substituted for plants, and gastropods would probably eat deer scat placed on it. But deer would probably not eat snail/slugs on Astroturf or on anything else.

References cited:

1. Coisy, Marc ; Brown, Sam P., ; Lafferty, Kevin D. ; Thomas Frederic. Evolution of trophic transmission in parasites: why add intermediate hosts? The American Naturalist 2003 August; 162(2): 172-181.

2. Auld, S.K.J.R. ; Tinsley, M.C. Review. The evolutionary ecology of complex lifecycle parasites: linking phenomena with mechanisms. Heredity 2015; 114: 125-132.

3. Windsor, Donald A. Biobrokers in parasite-host interactions. parasitesdominate.blogspot.com 2018 May 15. Post #18.

4. Parelaphostrongylus tenuis. Wikipedia https://en.wikipedia.org/w/index.php?title= Parelaphostrongylus_tenuis&oldid=835393860

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BIOBROKERS IN PARASITE-HOST INTERACTIONS

Post #18

BIOBROKERS IN PARASITE-HOST INTERACTIONS

Donald A. Windsor

I hypothesize that other species may be involved in parasite-host interactions.

In my previous post #17, I speculated that probiotics may be involved. But after further research revealed that the terms “probiotic” and “contrabiotic” are already in widespread use, so I will not use them.

Instead I will use the term “biobroker”. A broker facilitates transactions between sellers and buyers. A biobroker facilitates interactions between parasites and hosts. Biobrokers are probably microorganisms, but could be any other organisms, including other parasites.

Just as a financial transaction can occur without a broker, a parasite can infect/infest a host without a biobroker. However, some transactions are much smoother with a broker, because the broker may be able to work out a good deal for both participants.

Parasites must convince hosts to accept them. It seems that this convincing is usually of the “offer they cannot refuse” type of bullying. Parasites are usually host specific, showing that most other possible hosts are not convinced to accept the parasite and meet such overtures with rejection.

Evolution is all about evading extinction. Parasites may benefit their hosts, at the species level, by helping them survive. When a host species survives, its parasite species stand a better chance at surviving.

When a host species goes extinct, its parasite species will also go extinct, unless it is already in other species of hosts. A parasite species that has only one host species will survive its host species extinction only if it can find another species of host.

Here is where biobrokers can save the parasite species, by helping find new host species.

Parasites carrying the appropriate bacteria would be more successful infecting hosts compared to parasites without these bacteria. These bacteria would be probiotic for the parasites and contrabiotic for their hosts. Likewise, if the hosts were harboring bacteria that would thwart the parasites, those bacteria would be probiotic for the hosts and contrabiotic for the parasites. Biobrokers are both probiotic and contrabiotic and all gradations in between.

Right now, this hypothesis is pure speculation. I am looking for some real-world examples.

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PROBIOTICS AND PARASITES

Post # 17

PROBIOTICS AND PARASITES

Donald A. Windsor

Probiotic bacterial coatings on seeds enable plants to endure stresses, such as drought, and produce better crop yields. Indigo Agriculture is the company that is developing these coatings (1).

Could parasites, especially those that enter hosts’ bodies, naturally carry along their own probiotic bacteria? Probiotics might be the parasites’ way of preparing their hosts for enduring the stresses of their burden. Some parasites may even be able to be probiotics themselves. I have often wondered if parasites actually help their hosts bear the afflictions they cause.

In fact, a parasite has already been reported as being a probiotic. The haemoflagellate, Leishmania mexicana, protects its phlebotomine sand fly vector, Lutzomyia longipalpis, from the pathogenic bacterium, Serratia marcescens (2).

Could probiotics partially explain why some parasite species have intermediate hosts? Perhaps larval stages pickup probiotic bacteria from their intermediate hosts and carry them to their definitive hosts.

Probiotics may even explain host specificity and could offer a way to conserve parasites by providing new hosts.

Other microbes besides bacteria, such as fungi and even viruses, could also be probiotic.

Probiotics might also be useful in the therapy of pathogenic parasites. A probiotic is being tested as a treatment of white-nose syndrome in bats, an often fatal disease caused by a fungus (3).

I suspect that there is a lot more to the involvements of probiotics in ecosystems. I am now investigating.

References cited:

1. Anon. Less pesticide, more bacteria (That’s a good thing). Bloomberg Bussinessweek 2018 April 23; (4566): 25-26.

2. Sant’Anna, Mauricio R.V. ; Diaz-Albiter, Hector ; Aguiar-Martins, Kelsilandia ; Al Salem, Waleed S. ; Cavalcante, Reginaldo R. ; Dillon, Viv M. ; Bates, Paul A. ; Genta, Fernando A. ; Dillon Rod J. Colonisation resistance in the sand fly gut: Leishmania protects Lutzoyia longipalpis from bacterial infection. Parasites & Vectors 2014 July 23; 7: 329-338.

3. Oosthoek, Sharon. Bats to the wall. New Scientist 2018 April 21; 238(3174): 42-43.

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27 YEARS OF "EQUAL RIGHTS FOR PARASITES"

27 YEARS OF “EQUAL RIGHTS FOR PARASITES”

Post # 16

Donald A. Windsor

My catchy slogan, “Equal rights for parasites”, first appeared in the public domain in 1990 in Nature. Its most recent appearance was in 2017, 27 years later in the same journal.

Here is a bibliography of its published appearances over those years in my articles.

Windsor, Donald A. Heavenly hosts. Nature 1990 Nov 8; 348(6297): 104.

Windsor, Donald A. Guest Editorial. Equal rights for parasites. Conservation Biology 1995 Feb; 9(1): 1-2.

Windsor, Donald A. Editorial – Bird parasites. The Kingbird 1996 September; 46(3): 190-2.

Windsor, Donald A. Stand up for parasites. Trends in Ecology & Evolution 1997 Jan; 12(1): 32.

Windsor, Donald A. Equal rights for parasites. Perspectives in Biology and Medicine 1997 Winter; 40(2): 222-229.

Windsor, Donald A. Equal rights for parasites. BioScience 1998 Apr; 48(4):244.

Windsor, Donald A. Most of the species on Earth are parasites. International Journal for Parasitology 1998 December; 28(12): 1939-1941.

Windsor, Donald A. Parasites’ rights gaining ground. Nature 2017 December 21/28; 552(7685): 334.

A Google search for “equal rights for parasites” (quotes necessary) turns up numerous pages of citations. This slogan is well entrenched in the scientific literature. I certainly hope that it is heeded.

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EQUAL RIGHTS FOR PARASITES!

EQUAL RIGHTS FOR PARASITES!

Post #15

Donald A. Windsor

Conservation of parasites seems to be an increasing concern in the literature. Good.

My first involvement with this issue started at a Symposium on the Conservation of Biological Resources back in September 1990, at Cornell University in Ithaca, NY. The Society for Conservation Biology was formed just five years earlier and many of its founders were present. At dinner they were still conversing about conservation when I interjected a statement of caution. I warned that all day the talk was about conserving hosts; no mention was made of conserving parasites. I then spontaneously uttered, “How about equal rights for parasites?”

Most of the diners frowned and some even muttered “Good riddance”. However, one of the founders smiled and repeated “Equal rights for parasites” and complimented me on the catchy rhyme.

That was a pivotal moment for me and I often pondered it after the meeting. Some parasite species can go extinct when their hosts do, so if the hosts are saved, the parasites will be also. But at that time, antibiotics were being routinely administered to anesthetized wildlife because their paradigm was that wildlife should be healthy.

Viewed from the point of parasites, free-living wildlife are habitat. Forcing wildlife to be healthy is unnatural, a crime against nature. This was not a popular opinion, so getting my views published was difficult.

But, I got a powerful break when Nature, the world’s leading scientific journal, published my terse letter to the editor. Unfortunately, the editor assigned it a cutesy title. Here is an exact retype of that letter.

Nature 1990 November 8; 348(6297): 104.

Heavenly hosts.

SIR – In the attempt to save certain species from extinction, for example the California condor, the black-footed ferret and so on, how much attention is being given to their natural parasites?

When all of the last remaining members of a species are taken into captivity, they may lose their parasites, either by the drastic change in living conditions, by treatment from zoo veterinarians or by generations of captive breeding. When they, or their offspring, are then released back to the wild, will they be able to become reinfected? Some parasites are quite host-specific in the wild and may indeed become extinct when their natural hosts are gone.

“So what?” may be a typical reaction. But, if our goal is to conserve biological diversity, then indeed all species should be considered, not just those with the most outward appeal. Many hosts evolved or, better still, co-evolved with their parasitic burden. Perhaps they deserve each other.

Equal rights for parasites!

Windsor, Donald A.

PO Box 604

Norwich, New York, USA

In spite of the uninformative title, the response was very gratifying; even the media called.

Buoyed up by that feedback, I submitted many manuscripts to various journals, but most were rejected. However, a few did get accepted. In 1995 the editor of Conservation Biology invited me to write a guest editorial.

Windsor, Donald A. Guest Editorial. Equal rights for parasites. Conservation Biology 1995 February; 9(1): 1-2.

That led to another invitation and another publication.

Windsor, Donald A. Endangered interrelationships; the ecological cost of parasites lost. Wild Earth 1995-96 Winter; 5(4): 78-83.

More publications followed.

Windsor, Donald A. Stand up for parasites. Trends in Ecology & Evolution 1997 Jan; 12(1): 32.

Windsor, Donald A. Equal rights for parasites. Perspectives in Biology and Medicine 1997 Winter; 40(2): 222-229.

Windsor, Donald A. Equal rights for parasites. BioScience 1998 Apr; 48(4):244.

One reader even sent me a bumper sticker gaudily proclaiming “Equal Rights for Parasites”.

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COULD A PARADIGM ABOUT PARASITES EVER SHIFT THE TRADITIONAL PARADIGM OF ECOLOGY?

COULD A PARADIGM ABOUT PARASITES EVER SHIFT

THE TRADITIONAL PARADIGM OF ECOLOGY?

Posting # 14

Donald A. Windsor

When a tree falls in the forest and no one is around to hear it, does it make a sound?

When a paradigm shifts and no one in the scientific community notices, does it make any difference?

The tree question was asked by philosopher George Berkley in 1710. I ask my my paradigm question now. The vital role of paradigm shifts in science was explained by Thomas S. Kuhn in 1962.

My paradigm about parasites was published in 1998. I was advocating a paradigm shift. The newly formed concept in my paradigm turns ecology upside down and inside out.

Here is a brief backstory. My dissertation research involved parasites, but upon leaving school in 1966 my employment dealt with other subjects. When I retired in 1994, I was curious about what when on in parasitology during the previous 28 years. So I started reading the parasitology literature where I left off. When I finished in 1997 I experienced a shocking realization. Parasite species seem to be more numerous than their host species. Moreover, the important roles that parasites play in ecosystems seemed to be woefully understated and even vastly unrecognized.

Twenty years will soon have elapsed and, while my article has been cited 197 times, ecologistsists have not yet recognized this new paradigm as a shift. Maybe they never will. Regardless of what happens, I am getting too old to ever find out. Here is a brief synopsis.

The ruling paradigm in ecology holds that our biosphere is composed of free-living (non-parasitic) organisms, with parasites merely being pesky nuisances.

My paradigm contends that parasites are ubiquitous, insidious managers of our biosphere. They do not merely freeload off their hosts – parasites regulate their hosts. When competition and predation do not reign in host populations, parasites take over and prevent monocultures. The result is biodiversity. A corollary is even more astounding; some parasites enable their hosts to avoid extinction.

The validity of my paradigm can be tested, just as any other hypothesis can. If another planet, or even an asteroid, has life, but does not have parasites, then it will have few species and have large monocultures. My paradigm contends that parasitism is a property of life on Earth. Discovery of extraterrestrial life will reveal whether parasitism is a universal property of life.

I hope my paradigm becomes the current paradigm before we contaminate other worlds with our organisms and jeopardize this test.

References cited:

Berkley, George. A Treatise Concerning the Principles of Human Knowledge. 1710.

Kuhn, Thomas S. The Structure of Scientific Revolutions. Chicago, IL: University of Chicago Press. 3^rd Edition. 1996. 212 pages.

Windsor, Donald A. Most of the species on Earth are parasites.
International Journal for Parasitology 1998 December; 28(12): 1939-1941.

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