SamanthaM

Sex Makes the World go ‘Round

samantham — Fri, 21 May 2010 17:50:31 +0000

Sex broadly defined is a natural process combining genes from more than a single source into an individual cell. Sexual recombination in microbial communities refers to the breaking and combining of genetic material with the intent to reproduce beneficial generations. Sex in natural populations of microorganisms has to be understood using gene and genotype frequencies.
Genetic recombination and sexual reproduction is present in all microorganisms. For example, the sexuality of viruses is present in the reproduction of the influenza A virus making it a challenge to vaccinate individuals. Other examples of viral sexuality include dengue virus and hepatitus B virus. In prokaryotic sex, random association of alleles among certain groups of loci were found in N. memingitidis, S. pneumoniae, and S. aureus. Asexuality is common within the realm of microorganisms, however genetic recombination and sexual reproduction is very much present in these natural communities.
The disadvantage of asexual reproduction is that deleterious mutations would accumulate and the loss of mutation-free individuals would occur. Muller was one of the first to recognize the importance of spontaneous mutations in sex and sexual recombination. In observing the mutation rate per genome and per generation, the benefit and fitness of the mutation can be measured. In sexual recombination versus asexual reproduction, the mean fitness of sexual reproduction may be lower that that of asexual reproduction. However the initial cost of a lower fitness in sexual reproduction was compensated after several generations, when the fitness of sexual reproduction exceeded that of asexual reproductions when studying both of the communities. Therefore sexual reproduction may have a short-term cost, but results in a long-term benefit.
Deleterious mutations decrease the reproductive fitness of an organism. However if a deleterious mutation were to act independently from one another, natural selection will be efficient in eliminating them in sexual and asexual populations. However when deleterious mutations act antagonistically, it can have a smaller impact on the fitness of an organism and ultimately slow down the removal of them.
Sexual recombination has an initial loss in fitness, but reproduces to become more beneficial and fit. It is more able in the removal of deleterious mutations and is present in many kinds of microorganisms.

The prevalence and evolution of sex in miroorganisms- Jianping Xu

Big Brothers…

samantham — Wed, 21 Apr 2010 04:45:23 +0000

As a whole I really enjoyed the podcast provided by NPR. I think its really great that they were able to hit a lot of key points about the gut that people would find interesting. David was able to break down the complexity of microbial communities making it easy for someone without a scientific ear to comprehend what really is going on in there.

I’m glad that it is made known how durable the communities in our gut really care, but it is also really important to care for those communities and do out best not to tamper with them. As humans we rely greatly on this symbiotic relationship and we can’t just throw anything in our bodies trusting that it will just fix itself in the long run. We want to keep our apartments full after all.

One point that caught my attention is the discussion about how well the differing bacteria worked together in order to optimally thrive. David said that there are some altruistic bacteria that will sacrifice themselves in order to let a rare mutant take over. I’m interested in the kind of bacteria that can recognize this difference and is willing to step back and let the new guy take over. Then again, it could just be him simplifying it all.

Finally, the point that really got me concerned was the possibility of a bacterial fingerprint. I guess it’s neat and all that you can pinpoint a person just by what they eat and what pets they might have, and it would be a really cool way to get a family lineage… it’ll be a whole new level of those computer cd-rom things my uncle loves to invest in. The whole big brother aspect of it really creeps me out. Being able to pinpoint me from a glass that I drank from invades a whole new level of privacy. The internet is bad enough as it is, and I’m really uncomfortable with the fact that I can be tracked based on my bathroom habits alone. Everyone has to go at some point!
I hope it doesn’t take off in my era. Mystery is always a good thing!

Fixing Things

samantham — Wed, 21 Apr 2010 04:44:53 +0000

The evolution of virulence runs hand in hand along with the history of infectious diseases throughout centuries. The history of evolution helps explain the impact of infectious diseases in the past and helps guide modern medicine along the correct path of research. As a result of actions that were taken to control an infectious outbreak in the past, the evolution of important characteristics of pathogens were effected.

Recently the standing theory of the evolution of virulence, that disease organisms eventually should evolve toward benign coexistence with their hosts, has been investigated based on the principles of natural selection. This theoretical framework provides insight into the cause of infections of chronic diseases and an idea of what diseases can be prevented or cured by developing vaccines and antibiotics.

Use of antibiotics and vaccinations may lead to an increase in virulence if the virus or pathogen were to evolve. This leads to the idea of what can physically be done to the environment in which they thrive in order to reduce transmission as a disease control strategy. To illustrate, the virulence of a vector-borne transmitted disease is high due to the transmission from immobilized infected hosts, increasing the severity of diseases such as malaria and yellow fever. Thus, management of virulence of vector-borne diseases can be accomplished by vector proofing dwelling areas. So in the environments of those who are infected, it is important to vector proof those environments so that those diseases do not get transmitted.

Water-borne transmission is also highly virulent due to waste excretion and disposal. The severity of a diarrheal bacteria is correlated to the extent of which it is water-borne. Geographic comparisons support the virulence of diarrheal diseases because the severity of strains are disproportionately common where the potential for water-borne transmission is high. Thus the virulence of diarrheal pathogens can be evolutionarily managed by blocking water-borne transmission such as the decrease in virulence of Shigella and Vibrio cholerae after the water clean up in North America, South America, Europe, and Asia.

Microbial adaptation is going to happen regardless of the use of vaccinations, therefore the virulence will always change and evolve. However, we can only work towards pathogens becoming less virulent versus more virulent in making an effort to restrict transmission rather than treating the disease.

Evolution of virulence- Paul w. Ewald PhD Department of Biology, University of Louisville, Louisville, KY 40292, USA

Cheating is good.

samantham — Wed, 07 Apr 2010 04:47:40 +0000

In reading the paper “Developmental cheating in the social bacterium Myxococcus xanthus” by Velicer, Kroos, and Lenski varying generations of M. xanthus that were defective for fruiting-body development were observed, and the development of cheating as well as if they behaved as cheaters when mixed with their developmentally proficient progenitor (ancestor).

M. xanthus has several social behaviors such as aggregating cells into spore- producing fruiting bodies during starvation. They also have a social motility and predation, swarming together towards a prey and kill and degrade by the secretion of extracellular compounds.

When a defective M. xanthus is mixed with a proficient wild type, it was thought to have five possible outcomes. The first hypothesis is that the defective strain may sporulate with the same efficiency as it does in pure culture (null hypothesis H1). Secondly, a partially defective genotype’s sporulation in the presence of wild type may be inhibited even below it’s efficiency as it does in a pure culture. The third and fourth are the partial and complete rescue of the defective genotype by extracellular complementation in the presence of wild type. Finally, a developmentally defective genotype may produce more spores in the presence of wild type than would a neutrally marked wild type introduced at the dame initial frequency.

In the experiment that was performed, the developmental performance of six clones was compared to that of their wild-type ancestor DK1622. All six strains showed defects in spore production in relation to the DK1622. Therefore the spore production was measured of the evolved defective clones when they were mixed with their ancestor at an initial frequency of 0.01. the results were then compared to two possible hypothetical outcomes H1 and H2. The H2 hypothesis being an evolved cone behaving as would a neutrally marked variant of the wild type. As a result, the spore production in five out of the six clones were higher than predicted however sporulation of the sixth clone was hindered by the wild type majority.

Under H1, two out of the five showed partial complemention because they performed worse than expected under H2. However two of the cheaters (GVB208.3 and GVB214.3) performed better than expected under H2, showing moderate sporulation efficiencies as pure genotype, but also had an advantage over wild type when rare.

To further investigate this cheating, the two cheaters were mixed with their wild type progenitor at nine different initial frequencies. As a result, the initial frequency of both cheaters increased, however the total spore production of the pure wild type decreased thus doing an overall harm to the group performance. Both cheaters sporulated more efficiently than wild type at a low frequency, but the efficiencies dropped below wild type when the ratios were high.

Moreover, it was tested to see if a cheater can evolve from a single mutation, thus three genotypes that differ from their wild type progenitor bu a defined mutation. Because the fruiting bodies of M. xanthus involves several extracellular signals, the mutants what were observed were defective in the production of signal molecules. As a result, the mutants failed to contribute normal amounts of a particular developmental signal to the group, but like the previous two observed cheaters, they performed better than wild type when rare.

Therefore through all these experiments, it has been concluded that cheaters in myxobacteria can invade social groups and thrive.

This so Overwhelming

samantham — Sat, 13 Mar 2010 04:39:22 +0000

As I have stated before, microbial ecology and evolution is something that i have never thought about before. So in reviewing the Costs and Benefits of High Mutation Rates paper it was interesting to see how meticulous it is to identify simple features of an organism and how they evolved. All in all it makes me appreciate those who are willing to take the time and sift though all the phenotypic and genotypic characteristics of these organisms.
In reviewing this paper, it makes me think about the Fuzzy Species Among Recombinogenic Bacteria paper and how challenging it was for them to organize due to bacterial promiscuity. Maybe the analysis of the organisms in the might mutation rates paper could help the speciation organization. But like I said… this is new to me. Just a thought.

You’re Fat Because You Eat too Much

samantham — Fri, 26 Feb 2010 19:05:38 +0000

So basically the reason why you gain weight is because you eat too much. However it it theorized that the efficiency of how your body stores fat is based on the microbial ecology in your gut. We greatly benefit off of the 100 trillion microorganisms that reside in our gut, because they perform maintenance in our bodies that we would not be able to do without.
The differences in gut microbial ecology between humans may be an important factor effecting energy homeostasis. Those who are more susceptible to obesity may have more of an efficient gut microbial community promoting the extraction and the storage of energy from any given diet compared to the communities in lean individuals.
In order to study this theory further, mice with a mutation of the letpin gene allowing the mice to be tested susceptible to obesity and observe them compared to their lean mice siblings. Through this experiment, 3 soon to be mothers of the offspring, of the genetically altered litters were used to produce different litters. The offspring of this mating wave were observed and data was collected.
As a result the “obese”liter consumes 4% more than the lean siblings resulting in significantly greater body weights, as well as epidiymal fat-pad weights. Long story shirt the development of obesity in mice affects the relative abundance of the major gut bacterial content derived from the mother.
On the other hand, regardless of family membership, the cecal microbiota of obese mice had a statistically 50% reduction in Bacterioidetes and a significantly greater proportion of Firmicutes. The observation of 2 different mice (obese traits vs. lean traits) with the same body mass, however the “obese” mice had a significan’ty greater ratio of epididumal fat-pad mass to total body mass.
So even though you can blame your weight gain on your caloric intake, you can also take into consideration how well your gut is doing it’s job. You can thank your mom for that.

http://www.pnas.org/content/102/31/11070.full

I never really liked trees

samantham — Fri, 26 Feb 2010 19:04:47 +0000

In reading Fuzzy species among recombinogetic bacteria, it is frustrating how difficult it is to define species using DNA sequences. However, thus far I find it acceptable and easy to understand the the taxonomy of varying bacteria based on common phenotypic traits.
The title of this article is very appropriate knowing that due to the inter-species recombination the designed gene trees are nearly impossible to analyze and identify specifics. It is clear that the only way to properly cluster these genes is through the use of the multiple loci so that it can buffer against the results of inter-species recombination. The images of these trees are very difficult to understand. Even the trees in figure 2 are challenging even thought the contents are far simplified compared to the tree in figure 1.
Given the fact that the genetic trees were unsuccessful, I would like to see a tree based on a bacteria that is without or has little inter species recombination, so that I can better understand how these trees benefit towards microbial taxonomy. Furthermore, it was disappointing to become aware that there is another approach that has not been tackled. I think it would be a rewarding task to take on determining whether large populations of related bacteria can be divided into more specific clusters using specific molecular methods, or if groups of related bacteria fall into a genetic series where clear divisions do not exist. In examining a sequence-based, multilocus approach with large populations, the history of individual genes may be unnoticeable within inter-species recombination hopefully resulting into the merging of smaller clusters.
Within the 3 main clusters of N. meningitidus, N. lactamica, and N. gonorrhoea, the N. lactamica seemed highly inconsistent and most likely mis-identified. It is theorized that the use of the multilocus approach would be able to make the boundaries between N. lactamica and N. meningitidus less fuzzy.
There are various other angles that could be approached in order to name various types of microbial classes. However they have yet to be explored. It’ll be interesting to follow what new advances they make over the years with taxonomy and what approach will take them the furthest. It seems somewhat pointless to retry a technique that consistently fails with the availability of other alternatives that could benefit this area of study. Maybe in this particular line of study, a more simple type of bacteria with less inter-species recombination could be analyzed and worked up from there rather than picking apart a complicated and unreliable type like Neisseria.

Hot Getaway

samantham — Wed, 10 Feb 2010 04:43:42 +0000

Whitaker’s paper concentrates on the geographic barriers that are involved with the Sulfolobus species. Being extremophiles, this species reside in isolated locations that are easily targeted.

In relation to the Baas-Becking hypothesis, everything is everywhere, that the environment selects, the data collected in this research is supportive. Given the environment of these hot springs located all over the world, there is something that thrives in that environment. The research shows that there may be slight genetic variations of the species Sulfolobus, but it is still present and make it their habitat.

The reason why I feel that this data is supportive is due to my understanding of the hypothesis. Something can be found almost anywhere you look, and in these extreme environments like a hot spring, these microorganisms can be found.

I feel like they did a wonderful job of gathering base information to get a general result of the species’ variance and geographic barriers and locations. It is clear that there is still many more specifics that are to be discovered, but this overlook of these characteristics are satisfying. To further research this experiment, other environments could be sought out and more thoroughly compared.

Vanity

samantham — Tue, 02 Feb 2010 07:45:37 +0000

So my name is Samantha and I’m a former chem now microbio major. I am in this class because it was an option for a class requirement towards my major. I never really thought too much about microbial ecology, but I’m super excited to learn about it!!
Vanity seems to be a long running theme in my family. My mother, my mother’s mother, and so on, are all very particular about the way they present themselves. All through my childhood I would learn about the various tricks and remedies they would use to stay beautiful. As a result, I too am interested in the beauty of a person and how to hold onto that youthful bounce, shine, and glow we’re all blessed with at birth.
Therefore, in the long run, I want to create a line of hair and skin care products that ultimately help fight the process of aging for both men and women.
If I can boost someone’s self esteem by helping create a girl’s favorite shade of shimmering lip gloss that instantly makes her feel that much prettier… WHILE working to prevent the fine lines that form around her mouth as she ages… SO that she can continue wearing that same shade decades later… BECAUSE her lips are STILL full and plump like they were in her 20’s when she first discovered HER one thing that gives her a boost of every time she puts it on…

I’d be a very content girl.

Hello world!

samantham — Thu, 28 Jan 2010 06:24:36 +0000

Welcome to Micropopbio.org. This is your first post. Edit or delete it, then start blogging!