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Throughout the body, resident microbiotas are important for human health because they occupy niches that might be otherwise taken by pathogenic microorganisms. For instance, Lactobacillus spp. are the dominant bacterial species of the normal vaginal microbiota for most women. lactobacillus produce lactic acid, contributing to the acidity of the vagina and inhibiting the growth of pathogenic yeasts. However, when the population of the resident microbiota is decreased for some reason (e.g., because of taking antibiotics), the pH of the vagina increases, making it a more favorable environment for the growth of yeasts such as Candida albicans . Antibiotic therapy can also disrupt the microbiota of the intestinal tract and respiratory tract, increasing the risk for secondary infections and/or promoting the long-term carriage and shedding of pathogens.

  • Explain the difference between cooperative and competitive interactions in microbial communities.
  • List the types of symbiosis and explain how each population is affected.

Taxonomy and systematics

Assigning prokaryotes to a certain species is challenging. They do not reproduce sexually, so it is not possible to classify them according to the presence or absence of interbreeding. Also, they do not have many morphological features. Traditionally, the classification of prokaryotes was based on their shape, staining patterns, and biochemical or physiological differences. More recently, as technology has improved, the nucleotide sequences in genes have become an important criterion of microbial classification.

In 1923, American microbiologist David Hendricks Bergey (1860–1937) published A Manual in Determinative Bacteriology. With this manual, he attempted to summarize the information about the kinds of bacteria known at that time, using Latin binomial classification. Bergey also included the morphological, physiological, and biochemical properties of these organisms. His manual has been updated multiple times to include newer bacteria and their properties. It is a great aid in bacterial taxonomy and methods of characterization of bacteria. A more recent sister publication, the five-volume Bergey’s Manual of Systematic Bacteriology , expands on Bergey’s original manual. It includes a large number of additional species, along with up-to-date descriptions of the taxonomy and biological properties of all named prokaryotic taxa. This publication incorporates the approved names of bacteria as determined by the List of Prokaryotic Names with Standing in Nomenclature (LPSN).

Classification by staining patterns

According to their staining patterns , which depend on the properties of their cell walls, bacteria have traditionally been classified into gram-positive, gram-negative, and “atypical,” meaning neither gram-positive nor gram-negative. As explained in Staining Microscopic Specimens , gram-positive bacteria possess a thick peptidoglycan cell wall that retains the primary stain (crystal violet) during the decolorizing step; they remain purple after the gram-stain procedure because the crystal violet dominates the light red/pink color of the secondary counterstain, safranin. In contrast, gram-negative bacteria possess a thin peptidoglycan cell wall that does not prevent the crystal violet from washing away during the decolorizing step; therefore, they appear light red/pink after staining with the safranin. Bacteria that cannot be stained by the standard Gram stain procedure are called atypical bacteria . Included in the atypical category are species of Mycoplasma and Chlamydia , which lack a cell wall and therefore cannot retain the gram-stain reagents. Rickettsia are also considered atypical because they are too small to be evaluated by the Gram stain.

Questions & Answers

what is the difference between prokaryotic and eukaryotic?
Brian Reply
how many types of cell
Brian Reply
Two PLANT AND ANIMAL CELL
Shafi
actually we have two major types eukaryotic and prokaryotic eukaryotic may me unicellular as yeast or multicellular as plant ,animal, algae,fungi prokaryotic as bacteria
Khaled
hi, what are the most important things i should focus on to passed this class
Mulbah
guys I know is out of topic but I really need help
Mulbah
Hi
Brian
hi, any tips on this subject
Mulbah
you only need to focus on your study and you should expand your time of studying if there is any blockage for you
Alieu
Hi dear any one can splain how it is made Collagen peptide
natural
It's made of many bonds and proteins that are used to block
Lee
the history of cell theory.
Usman Reply
what are the principle of gram staining?
Hussaina
gram positive bacteria have matrix 10% and murein 90% which consists of peptidoglycan about four layers (very thick). gram negative bacteria have matrix 90% and murein 10% which consists of peptidoglycan about 2 layers (thin)
Khaled
so in gram positive bacteria : purple stain is trapped make alcohol can't leach it in gram procedure so appear purple (violet) in gram negative bacteria : purple stain is leached by alcohol and red stain of safranin after leaching give red colour appearance to gram negative.
Khaled
Name 4 Afb positive and negative bacteria?
sujay Reply
e coli staphylococcus streptococcus pseudomomas
Matilda
what invention
MALAMI Reply
?
Teressa
learn about micro bacterium tuberculosis
Dian
What are the conventional methods of microorganism detection?
Anna Reply
What are the convectional methods for microorganism detection
Anna
what is kidney stones. list some food that can heal it . How can kidney stone be cured?
dennis Reply
Are problèms related for crystal.
Abdullahi
is a calculus formed in the kidney
stephen
yes
tanya
eat light foods
Chandrima
just go tjorough bland diet
Chandrima
what are monomers, and is there a section for bacterial metabolism
SAM Reply
who is Aristotle?
soko Reply
Aristotle is the father of Biology.
Margrete
is a father of western philosophy
Kamaluddeen
father of classification of organisms
Williams
This is one of the greatest of the ancient Athenian philosophers
stephen
Sorry Aristotle was father of zoology
Sauri
father of classification of organisms
Williams
father of classification
Joy
Okay father of zoology
Joy
The bacteria that cause plague belong to the genes
Javid Reply
structure and functions of bacterial cell economic environment
Pavi Reply
what is haemaophilus influenzae
GALI Reply
what is the different between eubacteria and archaer bacteria
GALI
what the important of dna
Yunusa Reply
it act as hereditary material, coding for proteins and guide for life processes such as development reproduction etc
khan
Saving information from one generation to another, plus Structurale, fonctional, reproductive role
Ben
It's just structural, functional&
Nandkishor
liver is the largest organ of the body
maryam Reply
Liver is the largest internal organ within the human body but for this question the skin is the largest organ of the human body.
Margrete
Liver is the largest internal organ within the human body but for this question the skin is the largest organ of the human body.
Margrete
differences between prokaryotes and eukaryotes
Taiwo Reply
Eukaryotic cells contain membrane-bound organelles, such as the nucleus, while prokaryotic cells do not.
Margo
hello
usman
margo calvi....its your simple difference
Sadiqur
likely objective questions
Naa
what is largest Organ in the body
Dr
Skin is the largest organ in the body
Yadav
heart is the largest organ of the body
usman
liver is the largest organ in the body
maryam
liver is the largest organ in the body
maryam
skin
Janet
skin
Elyas
bilharzia
Elyas
i need formation
Elyas
liver is the largest organ in the body
maryam
Skin is the largest
Amin
skin
Amin
Practice MCQ 3

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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