Directional movement depends on the configuration of the flagella. Bacteria can move in response to a variety of environmental signals, including light (
phototaxis ), magnetic fields (
magnetotaxis ) using magnetosomes, and, most commonly, chemical gradients (
chemotaxis ). Purposeful movement toward a chemical attractant, like a food source, or away from a repellent, like a poisonous chemical, is achieved by increasing the length of
runs and decreasing the length of
tumbles . When running, flagella rotate in a counterclockwise direction, allowing the bacterial cell to move forward. In a peritrichous bacterium, the flagella are all bundled together in a very streamlined way (
[link] ), allowing for efficient movement. When tumbling, flagella are splayed out while rotating in a clockwise direction, creating a looping motion and preventing meaningful forward movement but reorienting the cell toward the direction of the attractant. When an attractant exists, runs and tumbles still occur; however, the length of runs is longer, while the length of the tumbles is reduced, allowing overall movement toward the higher concentration of the attractant. When no chemical gradient exists, the lengths of runs and tumbles are more equal, and overall movement is more random (
[link] ).
What is the peptidoglycan layer and how does it differ between gram-positive and gram-negative bacteria?
Compare and contrast monotrichous, amphitrichous, lophotrichous, and peritrichous flagella.
Key concepts and summary
Prokaryotic cells differ from eukaryotic cells in that their genetic material is contained in a
nucleoid rather than a membrane-bound nucleus. In addition, prokaryotic cells generally lack membrane-bound organelles.
Prokaryotic cells of the same species typically share a similar
cell morphology and
cellular arrangement .
Most prokaryotic cells have a
cell wall that helps the organism maintain cellular morphology and protects it against changes in osmotic pressure.
Outside of the nucleoid, prokaryotic cells may contain extrachromosomal DNA in
plasmids .
Prokaryotic
ribosomes that are found in the cytoplasm have a size of 70S.
Some prokaryotic cells have
inclusions that store nutrients or chemicals for other uses.
Some prokaryotic cells are able to form
endospores through
sporulation to survive in a dormant state when conditions are unfavorable. Endospores can
germinate , transforming back into
vegetative cells when conditions improve.
In prokaryotic cells, the
cell envelope includes a
plasma membrane and usually a cell wall.
Bacterial membranes are composed of phospholipids with integral or peripheral proteins. The fatty acid components of these phospholipids are ester-linked and are often used to identify specific types of bacteria. The proteins serve a variety of functions, including transport, cell-to-cell communication, and sensing environmental conditions. Archaeal membranes are distinct in that they are composed of fatty acids that are ether-linked to phospholipids.
Some molecules can move across the bacterial membrane by simple diffusion, but most large molecules must be actively transported through membrane structures using cellular energy.
Prokaryotic cell walls may be composed of
peptidoglycan (bacteria) or
pseudopeptidoglycan (archaea).
Gram-positive bacterial cells are characterized by a thick
peptidoglycan layer, whereas gram-negative bacterial cells are characterized by a thin peptidoglycan layer surrounded by an outer membrane.
Some prokaryotic cells produce
glycocalyx coatings, such as
capsules and
slime layers , that aid in attachment to surfaces and/or evasion of the host immune system.
Some prokaryotic cells have
fimbriae or
pili , filamentous appendages that aid in attachment to surfaces. Pili are also used in the transfer of genetic material between cells.
Some prokaryotic cells use one or more
flagella to move through water.
Peritrichous bacteria, which have numerous flagella, use
runs and
tumbles to move purposefully in the direction of a chemical attractant.
True/false
Bacteria have 80S ribosomes each composed of a 60S large subunit and a 40S small subunit.
What is the direction of water flow for a bacterial cell living in a hypotonic environment? How do cell walls help bacteria living in such environments?
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Microbiology is the scientific study of microorganisms
Ibra
the microorganisms in a particular environment (including the body or a part of the body).
Ibra
describe the bacterial cell
Akello
The biggest populations of microbes reside in the gut.other popular habitats include the skin genitals.The microbial cells and their genetic material ,the microbiome ,live with human from birth .