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Plant and Soil Sciences Faculty Book Gallery Plant and Soil Sciences
1996 So You Want To Be a Soil Microbiologist? Mark S. Coyne University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits oy u.
Follow this and additional works at: https://uknowledge.uky.edu/pss_book Part of the Environmental Microbiology and Microbial Ecology Commons, and the Plant Sciences Commons
Recommended Citation Coyne, Mark S., "So You Want To Be a Soil Microbiologist?" (1996). Plant and Soil Sciences Faculty Book Gallery. 1. https://uknowledge.uky.edu/pss_book/1
This Book is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in Plant and Soil Sciences Faculty Book Gallery by an authorized administrator of UKnowledge. For more information, please contact [email protected]. SO YOU WANT TO BEA SOIL MICROBIOLOGIST?
M.S. Coyne Department of Plant and Soil Sciences University of Kentucky
Copyright (©) 1996 by Mark Steven Coyne
All Rights Reserve St. Christopher Drive Press 2108 St. Christopher Drive Lexington Kentucky USA 40502-1118
To Sharon, Brian, and Lauren
SO YOU WANT TO BEA SOIL MICROBIOLOGIST?
M.S. Coyne Department of Plant and Soil Sciences University of Kentucky
1
So you want to be a Soil Microbiologist? Great! I can already see that we're going to get along famously. But you're not quite sure what a Soil Microbiologist is, or what a Soil Microbiologist does. No problem. That's what this book is for. 2
Let's take a look at typical Soil Microbiologists. On the surface, there's not much difference between them and what they study- soil (what else, no need for an advanced degree to answer that question). Both contain gas, some water, some minerals, and some organic matter (OM for short). ''Big deal," you say. But it's very important, because the organic matter in soil is alive (partly) and very small (mostly) and the organic matter in the Soil Microbiologist is alive (mostly), pretty big, and (key difference here) knows that it's alive (but sometimes during a hang-over wishes it weren't). 3
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A lot of people think Soil Microbiologists emerge, fully grown, from laboratory Petri plates. This is a misconception. ·This is wrong. Wrong! Wrong! Wrong! Wrong! Wrong! If you and I are going to get anywhere, we're going to have to start by looking at the history of Soil Microbiology. If you know where they've been, you can figure out where Soil Microbiologists are going in the future. So let's start. 5
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Soil Microbiologists have a long tradition dating back to the beginning of Agriculture. When the first cave man or cave lady noticed the relationship between ·plant growth and organic matter in soil, you could say they were the first Soil Microbiologists observing microbial activity like decomposition at work. 7
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Most people would agree, however, that our story really begins with Antonie Van Leeuwenhoek, a 17th century Dutch janitor and part-time lens grinder, who observed the first microbes through a primitive microscope.• 9
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A long time passed while scientists debated whether microbes were spontaneously generated or not. Once that was resolved (wouldn't you love to know what they decided?) we pick up our story again with Soil Microbiologists like Sergei Winogradsky, Louis Pasteur, and Selman Waksman. They began a great age in Soil Microbiology research starting in the mid 19th and early 20th century. ,.....-ro<
WHEN FAMOUS MICROBIOLOGIST's NAMES ARE MISPRONOUNCED
-""" ------·---
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SALMON SERGEI LOUIS WAKSMAN WINDYGRADSKY PASTURE
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Sergei Winogradsky was from Mother Russia, but he's called The Father of Soil Microbiology because: 1) he was a man; 2) he discovered lots of interesting things before anyone else did. Winogradsky invented the Winogradsky Column while studying the Sulfur Cycle. He investigated microbial growth on C02 and inorganic ions (Chemoautotrophy) and nitrification (the microbial process where NH4+ is converted into NOa-). Nitrobacter winogradskii is named in honor of him. 13
You know you've made it in microbiology when your friends name a microbe after you. You know what your friends really think about you when they name a foul, disease-causing microbe after you. ==> 14
Winogradsky investigated chemoautotrophic oxidation of ferrous iron. You could call him · the original Tin Man. 15
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Winogradsky also isolated Clostridium, the first anaerobic (without air) nitrogen-fixing (converting N2 to NHS) bacillus (rod-shaped bacterium) to be identified. 17
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Winogradsky's work with obligately anaerobic microbes was a direct influence on modern day research into anaerobic bacteria in special environments, like the animal rumen, by microbiologists like Robert Hungate. 19
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Now, this anaerobic, nitrogen fixing, bacterium wasn't named Clostridium winogradskii because Winogradsky was doing much of his work at an Institute named for another one of the great microbiologists of this era - Louis Pasteur (and his friends named Clostridium pasteurianum and other, nastier, microbes after him). Pasteur is a giant in the early age of Soil Microbiology. He.began life as a chemist (actually, a baby), but like most chemists with any sense, he soon took up microbiology. Pasteur is noted for the process which bears his name. He developed it to make French beer the best in the world. Naturally, this was impossible (which made Pasteur irritable). Pasteur also didn't like beer (which made him even more irritable). He was a difficult man to work with. ,....; N
THE TESTING OF PASTEURIZATION
LOUIS, MON DIEU. NON! NON! COME TO BED! ,______.I MUZT ZTAY AND ZAMPLE ANOTHER BOTTLE. EET EEZ FOR ~ FRANCE!
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The people who really suffered because Pasteur was both brilliant and irritable, were his students. One of Pasteur's best students, Thuillier, never became famous for developing the rabies vaccine with Pasteur. After years of thankless work inoculating French cattle and sheep with Pasteur's attenuated Anthrax vaccine, Thuillier went to Egypt at Pasteur's request and promptly died of cholera. When you're feeling blue, just think of Pasteur's students. You might be counting a thousand plates, but they were collecting a pint of rabid dog spit with mouth pipettes. • 23
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Pasteur said, ''Chance favors the well-prepared mind." 25
Pasteur must have only taken multiple choice exams 26
Pasteur hated Germany and Germans. One German whom Pasteur particularly hated was Robert Koch. Koch established his reputation by developing pure culture techniques (something Pasteur was never really good at - this also made him irritable). Pure culture was originally done on inconvenient substrates like potatoes or gelatin (from eyeballs). Koch's Postulates are named for Robert Koch. They are: 1. Isolate Anthrax bacilli from diseased guinea pig. 2. Infect healthy guinea pig with Anthrax bacilli. 3. Watch guinea pig die of anthrax. 4. Isolate Anthrax bacilli from dead guinea• pig.• 5. Repeat steps 1-4, 10,000 times. Being German, Koch was very thorough. ==> 1'- N
YOUNG KOCH
ROBERT~STOP PLAYING WITtl THOSE EYEBAl I S, COME BACK HERE, AND START STUDYING YOUR BOTANY. I .~
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It's a little-known fact that without the assistance of a woman, Koch's pure culture techniques would never have been so successful. Frau Angelina Hesse was married to one of Koch's assistants (who, mind you, were no less abused than Pasteur's students). She made exquisite desserts from extracts of red algae. One day, her husband Walther Hesse decided to grow something on one of these desserts. Agar agar was born; Koch's reputation was made; and Walther Hesse probably slept on the couch that night. (J\ N
ANOTHER IN THE SERIES a= DOMESTIC DISPUTES BETWEEN WALTHER AND ANGELINA HESSE THAT LEADS TO THE DEVELOPMENT OF AGAR-AGAR.
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Among the early Soil Microbiologists, collecting rabid dog spit and massacring guinea pigs were merely eccentricities. Elie Metchnikoff was a suicidal, sour-milk drinking Russian who thought that removing the large colon was a great idea (this was actually a very popular medical procedure in the Victorian Age). Metchnikoff also discovered Phagocytosis, which goes to show that insanity is no barrier to good microbiology. Metchnikoff believed that by consuming huge quantities of yogurt (milk fermented by Lactobacillus bulgaricus) one could prolong life. As it turns out, Metchnikoff kept his colon and died of a yogurt overdose at age 71. 31 32
So, there was Pasteur in Paris and Koch in Berlin. But there was also a great school of microbiology in Delft, The Netherlands which was led by Martinus Beijerinck. Now, Martinus Beijerinck was a stern man. A man who proved you can look like Frankenstein and still be a leader in your field. Beijerinck cultured the first isolates of symbiotic (in association with another organism) and asymbiotic (free living) nitrogen-fixing bacteria (Rhizobium and Azotobacter, respectively). Beijerinck is often attributed with this quote, "Everything is everywhere, but the environment selects." 33
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Meanwhile, in England, everyone knew that Alexander Fleming was a little different. They just couldn't put their finger on it. . Then, one day, Fleming announced that a fungus, · Penicillium, contaminating an old plate of Staphlococcus in his lab, was surrounded by a clear zone of dead and lyzed cells. He had discovered the first antibiotic, Penicillin. It didn't make him rich, but ·Fleming did get a knighthood, and he never threw anything away again.• 35 , r rn :s:- 36
This leads us to Selman Waksman. Waksman developed his love of Soil Microbiology at an early age in his native Russia. Later, at Rutgers University, Waksman and his research associate Dubos, discovered that a soil actinomycete, Streptomyces, had the same antibiotic properties as Fleming's Penicillium. 37
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Ultimately, Waksman's entire laboratory was devoted to discovering antimicrobial properties in soil microbes. Unlike Pasteur and Koch's students, all of Waksman's students became rich because the pharmaceutical industry was waiting for them with open arms. All, that is, except J.P. Martin, who decided to do some elegant, but unprofitable work, with fungi instead. 0'> ""
WAKSMAN'S STUDENTS WERE OFTEN UNWITTING PARTICIPANTS IN HIS MORE OBSCURE ACTINOMYCETE RESEARCH
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Waksman is often called The Father of American Soil Microbiology though, you never hear about his early work in microbial ecology, like the microflora of compost. 41
EARLY COMPOSTING . RESEARCH
I THINK IT's GETTING HOT IN HERE.
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You should be seeing a pattern develop. In Soil Microbiology, periods of slow, steady progress are separated by quantum leaps in technology and discovery. A quantum leap occurred when Leeuwenhoek developed the microscope. A quantum leap occurred when Koch developed pure culture techniques. A quantum leap occurred in another area, denitrification, when Payne in Georgia and Knowles in Canada simultaneously announced that acetylene blocked the reduction of nitrous oxide to nitrogen. Suddenly, Soil Microbiologists studying denitrification found they had the means of generating an almost limitless amount of nitrous oxide - laughing gas. The rest is history. 43
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During this period a class of organism was evolving which has direct effects on Soil Microbiology today. Of course, I'm speaking of organic chemists whose cleverly designed molecules have provided a wealth of research potential. Whole Soil Microbiology labs are dedicated to unraveling the decomposition of these organic molecules through such pathways as Ortho Cleavage, Meta Cleavage, and the lesser known Beaver Cleavage. 45
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Soil Microbiologists have also gone molecular. Initially, there were some problems with scale. ,.I' EARLY MOLECULAR BIOLOGISTS LACKED A SENSE OF SCALE
I SAID BRING A SCALPEL YOU BLOCKHEAD!
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Eventually, however, molecular genetics became fairly routine and its practitioners acquired the moniker (name) of Gene Jockey (molecular engineers) in MoBo (molecular biology talk). 49 so
The biggest fear of the general public is that careless splicing and dicing of microbial DNA could somehow lead to release of supremely harmful microbes in the environment. These fears are completely groundless (trust me, I've worked with these guys, and they're not that clever). If microbiologists could have made some supremely harmful microbe they would have already released it or accidentally dumped it down the sink. ,--; If)
TROUBLE IN THE GENETICS LAB
I ASSURE YOU ,.-/ LADIES AND GENTLEMEN, OUR RESEARCH IS HARMLESS. ©j---..,.------1
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Soil Microbiologists have contributed to mapping the genome of Escherichia coli. It is now possible to think about mapping the human genome and people are already trying to do it. This, too, is not without its consequences. 53 54
Perhaps, one day, it will become difficult to distinquish Soil Microbiologists from the microbes they study. WHEN MICROBIOLOGISTS GET 55 TOO CLOSE TO THEIR WORK
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GENETICIST VIROLOGIST
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If that happens, one day we may find that the microbes are studying us, rather than us studying them. 1' Vl
MICROBIAL DREAMS
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SPOCK! COULD THAT 1 STRANGE MULTICELLULAR 1M A BACILLUS CREATURE BE RESPONSIBLE FOR JIM. NOT THE DESTRUCT ION A DOCTOR. OF ALL THOSE ·~ PLANETS'? ~ BONES? THAT WOULD BE A ""' LOGICAL ASSUMPTION CAPTAIN. Hsc... 58
Wasn't that interesting? Hopefully, you can see what a colorful past Soil Microbiologists have had and what an exciting future they have in store for them. So, what now? Why don't we take a quick look at some of the organisms Soil Microbiologists study. 59
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On one end of the spectrum are unicellular animals called Protozoa. The best examples are Paramecium and amoebas. Protozoa have cell nuclei, so they're called Eucaryotes. 61
MS. PAC-MAN MEETS MR. AMOEBA
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Fungi are eucaryotes too. They reproduce by fragtnentation of filaments (hyphae), spore formation, and transfer of nucleic acid (sex). 63
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Although many fungi form filaments called hyphae, at least one group, the Yeasts, resemble bacteria in that they are unicellular. ll'l 1.0 WHY BUDDING MICROBES MUST .PART
DID I TELL YOU TO DO THAT? ARE YOU DEAF? I'VE GOTTA WHY DON'T YOU EVER GET OUT OF LISTEN TO ME ! '-...... HERE. IF I'VE TOLD YOU ""-. ••• ONCE I'VE TOLD --· YOU A HUNDRED TIMES • . • . . . . 0
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Unicellular microbes without nuclei are called Procaryotes. You wouldn't believe the diversity of different procaryotes in soil. The most important procaryotes are the bacteria. Soil Microbiologists partly classify and identify them based on their shapes. There are rod-shaped bacteria or bacilli. There are round-shaped bacteria • or COCCI. 1'- 1.0
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These Are Cocci. These Are Cocci on Drugs.
Don't Let This Happen To Your Cocci. ·l•
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Some bacteria like Hyphomicrobium or Caulobacter form long appendages called prosthecae. 69
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Some bacteria have spiral shapes and synthesize tiny magnets like Spirillum magnetotacticum. ==> ..-< 1'-
LOVE AMONG THE MAGNETOTACTIC BACTERIA
I'M SORRY LARRY. OUR POLARITIES DON 1T MATCH. YOU REPEL ME. \
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Some bacteria are shaped like commas. They are called Vibrios. Vibrio fischerii has the added bonus that it luminesces or glows. => 73
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Gene Jockeys have taken the genes for glowing from Vibrio fischerii and put them into all sorts of other bacteria and even plants. Having a glowing plant isn't particularly useful, except at Christmas, but it looks neat. Vl 1'-
MORE TALES OF LUMINESCENT BACTERIA
THEY CALL HIM SONNY BECAUSE HE'S SO BRIGHT. I I _.. ----- . \ / / \ I / ~ - - - -
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Many species of bacteria will occasionally swarm together and form a highly complex fruiting structure that you can see with the naked eye. 1'- 1'-
INEVITABLY THEY DISCOVERED THE CHAIRMAN WAS SIMPLY A HIGHLY DEVELOPED FRUITING STRUCTURE
THEY SAY THE CHAIRMAN AT VPI SWARMED LIKE THIS LAST YEAR.
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Naturally, Soil Microbiologists are constantly tempted to name the microbes they study. Unlike pets, it's not much use naming your microbes Bill or Ted or Fido. They don't come when you call, and besides, there are conventions against things like that. 79
The naming of Desulfomonas tiedjii is a good example. Dan Shelton, who originally isolated this microbe at Michigan State University, called it Pornobacterium (for obvious reasons if you've ever looked at micrographs of its reproduction). ==> 80
It wasn't long, however, before Pornobacterium was known by the more generic name of DCB-1. (for DeChlorinating Bacterium #1). It remained DCB-1 until Joe Suflita at Oklahoma University named it for his and Shelton's former boss James Tiedje. Which goes to show that if you can't do the work yourself, at least pay the bills, and maybe a bacterium will be named after you. 81 82
Several thousand times smaller than bacteria are obligate parasites called viruses. These are pesky creatures that are either alive or not depending on whether you think taking over another creature's genetic information to make a bazillion copies of yourself constitutes a life. / /Orl ~00 WHAT LYTIC .INFECTIONS ARE REALLY LIKE
ROGER! ROGER MY LOVE! HEY! THIS ISN 'T MY DNA~ I WANT MY I GOTTA GET DNA NOW! OUT OF THIS ' PLACE ROGER! STUFF IT IN! OOOH! WHY DO YOU STUFF IT IN! YOUR TAIL? LOVE YOUR CAPSID LOOK SO MY TAIL! ROGER! FAMILIAR? HEY! Q.UIT SHOVING! MY TAIL1 \
Msc. 84
Something you have to get used to, if you're going to become a Soil Microbiologist, is the jargon we speak. You'll soon find yourself inexplicably using jargon in the most unusual places. So, let's learn a few useful terms to get started. 85
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Taxis means movement in response to some gradient. This can be either positive (towards) or negative (away). A chocoholic exhibits positive taxis to Snickers Bars. Married men exhibit negative taxis toward their Mothers-in-Law. 1'- 00
NOTHING IS CERTAIN IN MICROBIOLOGY EXCEPT DEATH AND TAXIS
A ROD AMONG MEN MY FRIENDS. ~
HE'l; IS THAT FOOD OVER THERE? ~ LET'S GO EAT!
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· Chemotaxis, therefore, means movement in response to a chemical gradient - like caffeine. ==> 89
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Aerotaxis means movement in response to air or an oxygen gradient. 91 AEROTAXIS 92
Phototaxis means movement in response to a light gradient. 93
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In addition to naming microbes based on their shape, Soil Microbiologists also name them based on their tolerance to different environments. So, a Thermophile is a microbe that grows optimally at elevated temperatures. Thermophiles like it hot. ' 9 5
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Psychrophiles (or Cryophiles) are microbes that grow optimally at temperatures less than 4 oc. Psychrophiles like it cold. 97.
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An obligate aerobe is a microbe that requires air (oxygen) for growth and respiration. \_, ', 99
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A facultative anaerobe is a microbe which can grow in the presence or absence of oxygen. p z z )> r (/) .,0 ::0 IT1 (/) '"'0 :::0 p --; 0z 102
A big part of a Soil Microbiologist's time is spent growing microbes in pure culture to see what they are and what they do. So, you better get used to the idea of learning a lot of microbial physiology. / ,- '('(") ../ 0 // M BACTERIAL CULTURE
WHAT FASBINOER FILM IS IT? THE ONE-ARMED /MAN WALKS INTO THE FLOWER SHOP AND ASKS, •WHAT FLOWER STANDS FOR DAYS GO BY ..... II 104
Bacteria are clonal. In the absence of mutation, every bacterium in a colony is an identical copy of the first bacterium in that colony. 106
Another way of looking at it is that bacteria of today have direct links to bacteria at the dawn of time. Either that, or every bacterium is its own ancestor. ~ \
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Bacteria live to eat and reproduce and they reproduce by binary fission or doubling. 0'\ /0 ,....; WHY . MICROBES CAN 'r RAP
WE ARE BACTERIA .... WE LIKE TO CAUSE ---- ~ TROUBLE!
WE GET OURSELVES -- SOME FOOD .... ~ AND THEN WE START TO DOUBLE~
BOOM CHUCKA CHUCKA~ ... BOOM CHUCKA BOOM~
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Ideal bacterial growth can be described by the equation b = a x 2n where: b = the final bacterial population; a =the original bacterial population; n = the number of generations (you, your mom, and your grandma represent three generations). If Homer Simpson reproduced by binary fission, after 24 generations there'd be 16,777,216 Homer Simpsons. That doesn't seem so bad, 24 generations is a long time, 384 years if you figure 16 years per generation. To put it in context, though, on a good day the bacterium Escherichia coli can make 16,777,216 copies of itself in a little over three hours because its generation time is as little as 8 minutes. - ...-< ...-< ...-< 1248 LET"s BEGIN TO REPLICATE.
'((/ /111 I); ~ I 2 56 512 102<4 / -- WERE TOO iiRED TO COUNT NO MORE. 16 32 64 128 HURRY UP WE CAN "T BE LATE.
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The crucial event in biochemical evolution that made such rapid growth possible occurred when photosynthetic bacteria began evolving oxygen and aerobic bacteria evolved to use it. M ,.-{ ,.-{ FUNDAMENTALISM 3 BILLION BC , • 0 • 0 • 0 • .. • ., • •0 ~• 0 • ~ _. j; NE PLUS ULTRA! --=- C:::> ·~ ---
BOY, THOSE PHOTOSYNTHESIZERS, REALLY THINK THEY RE THE ACME OF CREATION.-
HEY! I CAN \~ BREATHE
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Respiring using oxygen makes a lot more energy for growth. But hey, I won't spoil physiology class for you by explaining why. \ 11~,
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The two most important elements microbes need are nitrogen and carbon. Many · bacteria use an enzymatic sequence called GS/GOGAT to take inorganic nitrogen and convert it into an organic form which they can use. GS/GOGAT stands for Glutamine Synthetase/Glutamine a Oxoglutarate Amino Transferase (so you can see why everyone uses the acronym). /r--:.. /, ,....,M ANNALS OF IMMOBILIZATION BY SAMUEL BECKETT
BECAUSE WE RE BUT WHY CAN'T WAITING FOR GOGAT. WE DO ANYTHING? ·o o / J ' ~ ,, c "0-Q () HC-N:H v~ HCH H c,.X':. I ~ ..vY.. HCH ~ Microbes also need carbon and lots of it. Given enough time and the right conditions, microbes will decompos~ any naturally occurring organic compound. Martin Alexander called this the Principle of Microbial Infallibility. If this weren't the case, substances would have accumulated to monumental proportions over geologic time. Can you imagine what it would be like if Soil Microbiologists weren't biodegradable? 119- 120 Decomposition isn't much more than Redox (reduction /oxidation) chemistry in action. Redox chemistry is just nature's way of moving electrons around and generating energy from the process. In nature, and especially in aerobic environments, organic and inorganic compounds that are reduced ( have a lot of electrons) get oxidized (lose their electrons). ===> .-l N ,...; ANNALS OF REDOX CHEMISTRY THE SWORD OF CHARLEMAGNE THE JUST IS FERRIC OXIDE, KNOWN AS RUST. 'I, CAN I INTEREST YOU IN SOME RUST-OLEUM MY FRIEND? ~ f1Sc.. 122 Because sources of electrons in soil are usually scarce (no hopping to McDonald's for a midnight snack in the microbial world) this means that competition among microbes for food and energy is intense. ' 123 r I 1I ~ 0- \ :::0 0 CD )>- \ r 0 0 -o~ rn -1 -1 - - 0- v c..~- z ~g~~~::0 _...... ~~ -o>o~ >Z;;o-i::O)> ~ rz • p-i -1 :I: 1"'1 ~ " - 124 In the microbial world everyone regards everyone else as lunch. All, that is, except photoautotrophs (algae and photosynthetic bacteria) who get their energy from sunlight and carbon from C02. Photoautotrophs, consequently, are the main course in many microbial diets. But microbes aren't fussy. Bacteria eat bacteria and fungi, nematodes (round worms) and protozoa eat bacteria, and certain fungi eat nematodes. -u ,.,::0 0 ~ 0 :::u ~ ,.,:::u -< ,.,:::u r )> -t 0- z (/) :c -u 126 Well, that's the end of our brief tour. But I can see one last question forming in your mind. "Is it going to be fun, exciting, and just a little bit dangerous?" you ask. You bet. Looking at microbial competition is just one of the exciting things Soil Microbiologists do. They also hunt specific microbes with gene probes. .r-:. /. N / .--< HAZARDS OF MICROBIAL LIFE ~ I / \ % ~ I / \ ;;tiJ! ~ ~ ~ /.. ~\ ~~' ' (';, WATCH OUT! " !Jh / IT'S THOSE \ BALLISTIC / TRANSFORMING "\/ ELEMENTS I AGAIN! ..-... 0 PESKY MOLECULAR BIOLOGISTS! MSc. 128 Soil Microbiologists battle rogue composting facilities. 129, \ ~ ~:;; :J:~ IT1 ::0"11m-., > ::oo ~ 1"1)> ::0 I c - A big branch of Soil Microbiology is devoted to harnessing Rhizobium as better inoculants for legume growth. \ ' 131 ,~ r r I CD ,:::0 0 ,_.z 0 () c r ):> z --f :r:8AJ() (/) N-1 o.9 CDc:m g:U ·8 132 More than a few Soil Microbiologists have been called on to save sewage treatment plants that have run amuck. ~.------~ .-< WHEN ANAEROBIC DIGESTERS GO BAD y "' .r ...... ---....._ -· ,. ~ NEW TOWN SEWAGE TREATMENT RESISTANCE IS M ij QO THEY'vE GOT WILSON USELESS! MAYOR AND SAY THEY WON'T I ._WE HAVE YOU TAKE THIS GARBAGE ~- SURROUNDED! ANY MOR - ...... / \ Lf !1SC- 134 There are literally hundreds of different things to do as a Soil Microbiologist- and it's never, never boring. Trust me. Next time you're having lunch with a Soil Microbiologist, ask them what they do. You'll be amazed. ==> ()- :::0 0 CD 0 5 -G) 136 Please Rewind For the Next User. <==