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| 9372551234 | peptidoglycan | A polymer composed of modified sugars cross-linked by short polypeptides. This molecular fabric encloses the entire bacterium and anchors other molecules that extend from its surface. | 0 | |
| 9372551235 | Gram stain | A technique that allows scientists to categorize many bacterial species according to differences in cell wall composition. | 1 | |
| 9372551236 | Gram-positive | These bacteria tend to have simpler walls with a relatively large amount of peptidoglycan. | 2 | |
| 9372551237 | Gram-negative | These bacteria tend to have less peptidoglycan, are more structurally complex, with an outer membrane that contains lipopolysaccharides (carbohydrates bonded to lipids). | 3 | |
| 9372551238 | capsule | A dense and well-defined sticky layer of polysaccharide or protein that surrounds the cell wall of many prokaryotes. | 4 | |
| 9372551239 | endospore | A resistant cell created by certain bacteria that allows it to withstand harsh conditions. The original cell produces a copy of its chromosome and surrounds that copy with a tough multilayered structure, forming the endospore. | 5 | |
| 9372551240 | fimbriae | hair-like appendages that allow prokaryotes to stick to their substrate or to one another. | 6 | |
| 9372551241 | pili | Appendages that pull two cells together prior to DNA transfer from one cell to the other; tend to be longer and less numerous than fimbriae. | 7 | |
| 9372551242 | taxis | A directed movement toward or away from a stimulus, from the Greek "taxis", to arrange. | 8 | |
| 9372551243 | nucleoid | A region of cytoplasm containing the prokaryote's genetic material; not enclosed by a membrane. | 9 | |
| 9372551244 | plasmids | Smaller rings of independently replicating DNA molecules that only carry a few genes, found in prokaryotic cells, in addition to its single chromosome. | 10 | |
| 9372551245 | transformation | The genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings. | 11 | |
| 9372551246 | transduction | Phages carry prokaryotic genes from one host cell to another. | 12 | |
| 9372551247 | conjugation | DNA is transferred between two prokaryotic cells (usually of the same species) that are temporarily joined. In bacteria, the DNA transfer is always one-way: One cell donates the DNA, and the other receives it. | 13 | |
| 9372551248 | Obligate aerobes | Prokaryotes that must use oxygen for cellular respiration, and cannot grow without it. | 14 | |
| 9372551249 | Obligate anaerobes | Prokaryotes that are poisoned by oxygen, and live by fermentation or anaerobic respiration. | 15 | |
| 9372551250 | Anaerobic respiration | A form of respiration in which substances other than oxygen, such as nitrate or sulfate ions accept electrons at the "downhill" end of electron transport chains. | 16 | |
| 9372551251 | Facultative anaerobes | Prokaryotes that use oxygen if it is present but can also carry out fermentation or anaerobic respiration in an anaerobic environment. | 17 | |
| 9372551252 | Nitrogen fixation | The process, carried out by some cyanobacteria and some methanogens, of converting atmospheric nitrogen to ammonia, which can then be incorporated into amino acids and other organic molecules. | 18 | |
| 9372551253 | extremophiles | Prokaryotes that survive in extreme conditions, from the Greek "lover" of extreme conditions. | 19 | |
| 9372551254 | Extreme halophiles | Prokaryotes that live in highly saline environments, from the Greek "halo", meaning salt. | 20 | |
| 9372551255 | Extreme thermophiles | Prokaryotes that live in very hot environments, from the Greek "thermos", meaning hot. | 21 | |
| 9372551256 | methanogens | Archaea that release methane as a by-product of their unique ways of obtaining energy. Many use carbon dioxide to oxidize hydrogen gas, which produces both energy and methane waste. | 22 | |
| 9372551257 | decomposers | Prokaryotes that break down dead organisms as well as waste products, thereby unlocking supplies of carbon, nitrogen, and other elements. | 23 | |
| 9372551258 | symbiosis | An ecological relationship in which two species live in close contact with each other. | 24 | |
| 9372551259 | host | The larger organism in a symbiotic relationship. | 25 | |
| 9372551260 | symbiont | The smaller organism in a symbiotic relationship. | 26 | |
| 9372551261 | mutualism | An ecological interaction between two species in which both benefit. | 27 | |
| 9372551262 | commensalism | An ecological interaction in which one species benefits while the other is not harmed or helped in any significant way. | 28 | |
| 9372551263 | parasitism | An ecological relationship in which one species harms another species. | 29 | |
| 9372551264 | parasite | The species that harms the other species by eating its cell contents, tissues, or body fluids of its host. | 30 | |
| 9372551265 | pathogens | Parasites that cause disease. | 31 | |
| 9372551266 | exotoxins | Proteins secreted by certain bacteria and other organisms which cause disease. | 32 | |
| 9372551267 | endotoxins | Lipopolysaccharide components of the outer membrane of gram-negative bacteria. They are released only when the bacteria die and their cell walls break down. | 33 | |
| 9372551268 | bioremediation | The use of organisms to remove pollutants from soil, air, or water. | 34 | |
| 9372551269 | Chlamydias | parasites that live within animal cells (gram negative) | 35 | |
| 9372551270 | Cyanobacteria | Photosynthetic, oxygen-producing bacteria (formerly known as blue-green algae). | 36 | |
| 9372551271 | Halophiles | "salt-loving" archaea that live in environments that have very high salt concentrations | 37 | |
| 9372551272 | Thermophiles | Prokaryotes that thrive in very high temperatures | 38 | |
| 9372551273 | Methanogens | Prokaryotes that synthesize methane from carbon dioxide and hydrogen gas | 39 | |
| 9372551274 | Phototrophs | obtain energy from light | 40 |
