ECOL 182R 1st Edition Lecture 10 Outline of Current Lecture I Plantae II Land plants A History B Gametophytes vs sporophytes III Nonvascular plants IV Vascular plants V Angiosperms Outline of Current Lecture I Symbiosis II Recent research A DNA sequencing III Bacteria on animals IV Bacteria in animals V Bacteria in guts A Development B Preventing disease Current Lecture Symbiosis intimate association between unrelated organisms not necessarily beneficial Includes parasitism harmful and mutualistic relationships and others that are hard to categorize A symbiont is the smaller organism that lives in on the bigger one Microbial symbionts are everywhere not just in animals not just in bacteria Skin bacteria can protect against infection not all bacteria are harmful Why are we finding out so much NOW Less than 1 of bacteria can be cultured Meaning they re hard to work with find helpful info Many bacteria look alike even with electron microscopes So there s a very limited ability to investigate complex bacteria with just morphology Polymerase chain reaction PCR makes a lot of DNA out of very small amounts How it works take short DNA segments primers mix them with DNA from an organism The segments bind on either side and then add Polymerase to extend the DNA and you get copies of that segment Those copies serve as templates for more copies etc This is valuable because then you can visualize it and then sequence it You can see if they have a certain bacterium You can now work with this DNA DNA sequencing been around for a while Techniques that make it cheap and easy Makes sequencing a single bacterial gene from thousands of cells affordable It s valuable because you can see how frequent a bacterium is present The mammalian gut flora Fairly new The axenic NO gut microbes and gnotobiotic reduced and known number of microbial species mouse models Valuable because you can separate the difference of two mice with different bacterium and see the role of the bacteria The Human Microbiome project characterized all bacteria associated with humans 200 scientists at 80 institutions sequenced bacteria from 250 healthy people Complete in 2012 Samples from different parts of skin openings gastrointestinal tract Sequenced a single bacterial ribosomal gene that allows assignment to bacterial group Bacteria ON animals Human skin bacteria Found 1000 species of bacteria a trillion cells most non pathogenic not associated with the disease Amazing variation in the communities Ex Manubrium high chest with front forearm completely different bacteria Bacteria sweat because acid build up that acid environment makes it hard for pathogenic bacteria to establish Some skin bacteria secrete antimicrobial substances that keep pathogenic bacteria from domination Common theme pathogens are common in on healthy individuals just aren t causing disease Bacteria on beewolves Their nests are moist risk of bacterial fungal infection They carry bacteria on their antennae It s called actinobacteria a group known for producing effective antibiotics It s transmitted from mother to offspring Lays egg on bee and rubs antennae around cell to coat it with bacteria As adults the larvae chew out of cocoon and get the bacteria on their antennae Each species of beewolf has its own species of bacterium Bacteria lives inside pockets in antennae The bacterium s role To prevent other bacteria from getting to the larvae How would you test that idea Take out the bacterium clean out that chamber take out the lining sterilize it then put the larvae back in and then see how they do The cocoons will die of fungal bacterial infections Bacteria IN animal cells Lots of viruses some protists and some bacteria are parasitic symbionts of human cells In general bacterial cell pathogens are less dangerous now than they were before antibiotics Ex the bacterium Rickettsia prowazekii is carried by human lice and causes typhus Typhus causes fever aches pains death Epidemics of it were common usually followed wars natural disasters where lice density was high During WWI typhus caused 3 million deaths Thousands of inmates in concentration camps were affected too Can be effectively treated with antibiotics now In insects many bacteria live inside cells and then transmitted from mother to offspring in egg cytoplasm They re not transmitted contagiously from one insect to another Can you guess anything about the relationship between insect bacterium from know how the bacteria are transmitted Mother passes it to offspring can mean that it s probably beneficial Many of these interactions are beneficial for both partners mutualism Aphids plant sap sucking insects live on a diet of mostly sugar water with low levels of amino acids many aren t even the kind they need to make proteins How do they survive on such a lousy diet They house bacteria on special organ bacteria synthesize essential amino acids they can t reproduce without that bacteria Aphids bacteria have evolved together Bacteria in guts Historical characterization of gut bacteria is commensal beneficial to bacteria with no effect on us We assumed they re just there and occasionally bad ones get in there make us sick In humans what s in there 1000 species 100 trillion cells We carry more bacterial cells than human cells Which is about 2 5 pounds of our weight Babies pick up some bacteria as they leave birth canal Mother s milk has 600 species and necessary sugars to establish the bacteria in the baby s gut In the first few years more more bacteria are acquired What do they do inside us Make vitamins digest complex starches Help the gut immune system develop normally Keep pathogens from making us sick Reduces stress to be determined My bacteria are not your bacteria Communities of bacteria differ There s an environmental component some similarity within a household There s a genetic component too Identical twins have more similar than fraternal twins Obese people who become thin got a thin person s bacterial community Nutrition differs depending on what your bacteria are Study done in Malawi on 317 pairs of twins living in same house 43 were both well nourished 7 both malnourished 50 1 was well nourished 1 was not In cases where twins different the gut flora differed as well Does this tell us that the gut flora is responsible Critical experiment Got samples of gut flora from the twins where 1 was malnourished the other wasn t Mice with the gut flora from the malnourished children lacked the ability to make