Submitted by tanteidaiko t3_zdpa6g in askscience
Have just started a career as a Medical Technologist. And this is the first time Im exposed to the term serotypes - e.g. in Salmonella, Dengue viruses, etc.
What I can't seem to understand or find out is if serotypes are different from phenotypes and genotypes. Are the antigenic expressions linked to the genotypes? Or are the gene entirely the same among species and the antigens are expressed based on a different mechanism?
Great answer. The serotypes, in a way, are a phenotype - one that is "seen" by the host's antibody response. Like a negative image, perhaps. The genotype codes for that "phenotype" in a way that we haven't quite figured out yet (ie, there aren't commonly PCR tests, or MALDI data for serotypes, but there are groups working on them almost tirelessly).
We actually can do serotyping by sequence for a bunch of bacterial pathogens. Neisseria meningitidis, for one. Pasteurella multocida for another. Those are two I've done in the past couple months.
But a phenotype can be slightly different than the genotype, right? I mean depending on epigenetic factors and environmental factors.. Or am mistaken here?
You can't compare phenotype and genotype in this manner. Just like you can't play an instrument you don't have, you can't express genes that aren't in your genotype. Epigenetics will basically modify what genes are expressed. It will get you from phenotype A to phenotype B if you will, but saying it is "different from your genotype" doesn't make sense. All your possible phenotypes are contained in your genotype.
I think this the interesting and crucial point. Are serotypes mainly influenced by genotypes or are there epigenetic factors at play also.
I have done many Dengue E1 Sequencing and I frequently BLAST the sequences. We do see that these sequences can be catergorised into the serotypes themselves. So does mean that the sequences, and therefore genotype, confers the serotypes?
Not familiar with the lingo. Blast, is that a method in itself?
Maybe I can ask a couple of questions if you have the time: Are you sequencing serotype, transcriptomics and DNA of white blood cells that are infected? And can you predict serotype from DNA? Or only from transcriptomics?
BLAST is an online sequence alignment tool by NCBI.
I am sequencing the genome of the Dengue virus itself that we extract from an infected person. And we are able to determine the serotype affecting a person via real time PCR itself. So we draw the patient's blood, spin it down into serums, then we do nucleic acid extraction to obtain the RNA. Then we do real time RT-PCR to detect the presence of any sereotype of the virus.
That's a very good question. Back when I was in the lab, serotypes couldn't be distinguished by sequencing but we seem to have moved towards being able to do that and the serotypes of strep have evidence for having a genetic basis:
Yeah they are. Mostly. Well, it gets weirdly complicated.
Top level. Yes. The isolate has some genotype, which determines its phenotype. The one we're interested in is the antigenic profile, which is to say those "things" that our immune system sees. Some are lipids, some are proteins, some sugars, etc. Our immune system responds in a certain way against a pathogen with one particular antigenic profile, and a somewhat different way against a different isolate of that same species if it has a different antigenic profile. Different isolates are of the same serotype if our immune system responds to them in the same way.
I say mostly, because our human genotype also comes into it. And some species have ways for individuals to hyper-mutate or randomly change parts of their antigenic profile. So serotype doesn't correlate with anything like virulence or antibiotic susceptibility, and is basically meaningless. There are also some species who don't cause an immune response. So they don't really have a serotype. And other species who all cause the same immune reaction, and don't really have serotypes either.
And here's the fun bit. The word "serotype" kind of means different things depending on the species. It's basically defined by the field. Decided at conferences. So there's no actual single true answer to your question. Which is why I say it gets weirdly complicated.
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Serotypes are a type of phenotype that is based on the antigens present on the surface of a microorganism, such as bacteria or viruses. These antigens, known as surface proteins, determine the immune response to the microorganism and can be used to classify and identify different serotypes.
Serotypes are different from genotypes, which are the genetic makeup of an organism. While genotypes are determined by the DNA sequence, serotypes are determined by the proteins on the surface of the organism.
In some cases, serotypes can be used to predict the virulence or susceptibility of an organism to certain drugs. For example, some serotypes of the bacterium Streptococcus pneumoniae are more likely to cause severe infections, while others are more susceptible to antibiotics.
Overall, serotypes are an important aspect of the study of microorganisms, and they can provide valuable information about their characteristics and behavior.
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feliciates t1_iz3cs0y wrote
Serotyping is a subtyping test based on differences in microbial (e.g., viral or bacterial) surfaces. Like salmonella is serotyped based on which type of O-Antigen and H-Antigen they have
Phenotype refers to the expressed features of an organism (that is, the way the genes are expressed). A genotype is the entire collection of an organism's genetic information. The genotype includes all the genetic information, regardless of whether it's being used and expressed or not.