the most abundant organisms on earth—don’t have skeletal, respiratory,circulatory, digestive, or nervous systems,because they are too small to need them
is the first test microbiologists use when they are identifying an unknown bacterium
they have a thick layer of a glyco protein called peptidoglycan on the outside of the cell wall
may restrict the movement of water out of the cell and allow bacteria to live in dry places, such as on the surface of your skin. In other cases, the capsule may be important in allowing the bacteria to bind to solid surfaces such as rocks or to attach to human cells.
A second type of structure that carries genetic information is a circular DNA molecule
Plasmids carry genes for specific functions. For example, metabolic plasmids carry genes enabling bacteria to break down specific substances, such as toxic chemicals; resistance plasmids carry genes enabling bacteria to resist the effects of antibiotics; and virulence plasmids carry genes that control how sick an infectious bacterium makes its victim.
is the process by which one bacterium transfers a copy of some of its genetic information to another
A bacterium transfers a copy of some or all of its DNA to another bacterium, giving the second bacterium genetic information it did not have before.
occurs when a kind of virus called a bacteriophage infects a bacterial cell.The virus reproduces inside the bacterial cell,and sometimes, inadvertently, the new virus particles are filled with pieces of bacterial DNA in addition to or instead of the viral DNA. When these viruses are released and infect new bacterial cells, the bacterial DNA can be inserted into the host bacterium’s chromosome, passing new bacterial genes to that bacterium.
is the process by which bacterial cells scavenge DNA from their environment. This DNA comes from other bacterial cells that have burst open, releasing their cellular contents. The circular chromosomes break into short lengths of DNA, which can then be taken up by living bacterial cells and inserted into their own chromosomes,potentially adding genes they did not originally have.
chemolithotrophs (Chemical inorganic feeders)
are able to use a completely different type of food as their source of energy: inorganic molecules such as ammonia, hydrogen sulfide, hydrogen, and iron. The most common inorganic feeders are the iron bacteria responsible for the brown stains that form on plumbing fixtures in regions where tap water contains high levels of iron. Sulfur bacteria are associated with iron bacteria, and are responsible for the slimy black deposits that you will probably find if you lift the stopper out of the drain in your bathroom sink.
photoautotrophs “Light self-feeders”
bacteria that use the energy from sunlight—contain chlorophyll and use light energy to convert carbon dioxide to glucose by photosynthesis. The floating mats of gooey green material that you see in roadside ditches are a type of photoautotroph called cyanobacteria.
chemoorganotrophs (Chemical organic feeders)
are bacteria that consume organic molecules, such as carbohydrates. You probably see the products of organic feeders every time you take a shower—they are responsiblefor the pink deposits on the shower curtain and otherdiscolorations on the floor of the shower. Most of the bacteria that live in and on your body are also organic feeders. Some compete with you to metabolize the food you eat. Others digest things you can’t digest or can’t eat.
disease-causing bacteria is very small compared with the total number of bacterial species,but some pathogens kill millions of people annually, despite advances in medicine and sanitation.
sexually transmitted diseases (STDs)
are caused by a variety of organisms, including bacteria, viruses, protists,fungi, and arthropods. Worldwide, more than 300 million people are newly infected each year.
tolerate extreme physical and chemical conditions, and the organisms that can live in these conditions, both bacteria and archaea
is an organism that lives in or on another organism, called a host, and damages it.
Viruses that infect birds don’t bind well to glycoproteins in human cells, making it difficult for bird viruses to infect humans.
However, a virus that infects humans and a virus that infects birds can meet in a pig cell, replicate, and get packaged together into anew virus capable of infecting humans.
an RNA-containing virus that also contains a viral enzyme called reverse transcriptase that uses a strand of viral RNA as a template to synthesize a single strand of DNA.