1. What are the three most common genetic recombination events that happen in bacteria? Explain each.
Explain its implication in virulence and antibiotic resistance.
Genetic recombination, also known as genetic reshuffling, involves the transfer of genetic
material between distinct organisms, resulting in the creation of offspring possessing trait combinations
distinct from those observed in either parent (Meshram et al., 2021, #207-224). This natural process can
be replicated in a laboratory setting. Recombination enhances genetic diversity in sexually reproducing
organisms, enabling an organism to exhibit novel functionalities. This process can occur in several ways,
but the three most common genetic recombination occurrences in bacteria are transformation,
conjugation, and transduction.
Bacteria undergo transformation when they pick up free DNA from their surroundings and
incorporate it into their genome. A bacterial cell absorbs external DNA in this procedure. The incoming
DNA could be from other bacterial cells being lysed (broken open) or from DNA being released into the
environment. Bacterial transformation enables them to acquire virulence factors, which are genes or
gene clusters that improve their potential to cause disease. Bacteria, for example, can acquire genes
coding for toxins, adhesins, or other features that boost their ability to colonize and cause harm to a
host. Transformation is an essential mechanism for acquiring antibiotic-resistance genes. Bacteria can
take up DNA fragments harboring resistance genes from their surroundings, allowing them to withstand
antibiotic exposure.
Transduction involves the transfer of genetic material from one bacterium to another using a
bacteriophage. During the lytic cycle of a bacteriophage, the virus can accidentally package bacterial
DNA instead of its genetic material. When this phage infects another bacterium, it injects this packaged
bacterial DNA into the new host, resulting in bacterial gene transfer. With bacteriophages, transduction
can transfer harmful traits like virulence factors and antibiotic resistance genes between bacteria. This
process aids in the evolution of harmful bacteria and contributes to the horizontal spread of antibiotic
resistance.
Bacterial conjugation, also known as bacterial sex, is a way bacteria share genetic material
(Virolle et al., 2020). It happens when a donor cell with a special plasmid connects to a recipient cell
using a structure called a pilus. The plasmid DNA is then passed from the donor to the recipient through
this connection. Conjugation helps spread harmful traits among bacteria, like turning non-harmful
bacteria into harmful ones. This process is important for creating more aggressive bacteria and spreading
antibiotic resistance. Plasmids with resistance genes can move from resistant to susceptible bacteria,
making resistance spread quickly.
2. Choose one species of bacteria and describe its nutrition and growth requirements. Any species will
do.
Borrelia burgdorferi is a pathogenic spirochete that causes Lyme disease, a vector-borne illness
transmitted through the bites of infected ticks. The bacterium lives in ticks' midguts and is transmitted to
mammals during blood meal. Its specific life cycle and the complex transmission between arthropod
vectors (ticks) and vertebrate hosts, primarily mammals, including humans, are intimately linked to its
nutritional and growth requirements (Tatum & Pearson-Shaver, 2023).
Borrelia burgdorferi is microaerophilic, which means it thrives in situations with lower oxygen
levels than the surrounding environment. This pathogenic spirochete sources its nutrients in ticks
because ticks provide a unique environment for the bacterium. It relies on the nutrients present in the
tick's blood meal, including amino acids and other essential components. Its microaerophilic
characteristic is critical for survival in the midgut of ticks, where it goes through numerous stages of its
life cycle. After being transmitted to a mammalian host, Borrelia burgdorferi adapts to a variety of
environmental circumstances, attacking a variety of tissues and organs. Its contact with the extracellular
matrix in host tissues is critical for spread. The slow growth rate of the bacterium adds to its persistence
in the host, evading the immune system and causing chronic infections. Spirochetes, spherical bodies,
and biofilm-like clumps are all part of the complicated life cycle (Lakum & Stevenson, 2005, #173-179).
3. Choose one species of bacteria and describe how it can be controlled using physical and chemical
ways to control microorganisms
Controlling Borrelia burgdorferi, the bacterium that causes Lyme disease, requires a combination
of physical and chemical measures to manage and limit the microorganism's spread.
The tick serves as a conduit for vector-borne diseases such as B. burgdorferi, allowing them to
move from reservoir hosts to human hosts. The ability to minimize all diseases transmitted by that vector
is one advantage of targeting the vector rather than a single infection (Bernard et al., 2020). Avoiding
ticks and eliminating any signs of these vectors is a way to control the transmission of Borrelia
burgdorferi. Wearing long-sleeved clothing, performing tick inspections regularly, removing ticks with
tweezers, keeping lawns in good condition, clearing leaf litter, and erecting physical barriers such as
gravel or wood chips to separate wooded areas from recreational areas are some fundamental physical
control methods.
Chemical control methods involve the use of insecticides, like utilizing acaricides (tick-killing
chemicals) on vegetation or treating clothing with permethrin. Rodent control is also crucial. Since ticks
often feed on small mammals like mice, reducing the population of these host animals can indirectly
limit the prevalence of Borrelia burgdorferi.
Vaccination is another method to control the bacterium. Multiple diseases are frequently carried
by Ixodes ticks. A vaccination that targets the vector could prevent numerous diseases at once. In the
laboratory, tick antigens have been demonstrated to be effective in preventing successful tick feeding
(Bernard et al., 2020). A commercial vaccine against the Bm86 protein found in Boophilus ticks has
successfully protected cows from tick feeding (Fragoso et al., 1998).
A thorough approach to controlling Borrelia burgdorferi involves a combination of physical
measures to reduce exposure to ticks, especially tick immunity. This way, we can mitigate the risk of
acquiring and dispersing Lyme disease.
References
Bernard, Q., Phelan, J. P., & Hu, L. T. (2020, November 4). Controlling Lyme Disease: New Paradigms for
Targeting the Tick-Pathogen-Reservoir Axis on the Horizon. NCBI. Retrieved November 26, 2023,
from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7744311/
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Retrieved November 25, 2023, from
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p/a/genetic-variation-in-prokaryotes
Lakum, K. V., & Stevenson, B. (2005, February). Carbohydrate utilization by the Lyme borreliosis
spirochete, Borrelia burgdorferi. Borrelia burgdorferi, FEMS Microbiology Letters, Volume
243(Issue 1), 173-179. https://doi.org/10.1016/j.femsle.2004.12.002
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Retrieved November 25, 2023, from https://www.merriam-webster.com/dictionary/transduction
Meshram, S., Bisht, S., & Gogoi, R. (2021). Biopesticides: Volume 2: Advances in Bio-inoculants (A.
Rakshit, V. S. Meena, P.C. Abhilash, B.K. Sarma, H. B. Singh, L. Fraceto, M. Parihar, & A. K. Singh,
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Tatum, R., & Pearson-Shaver, A. L. (2023, July 17). Borrelia Burgdorferi - StatPearls. NCBI. Retrieved
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Virolle, C., Goldlust, K., Djermoun, S., Bigot, S., & Lesterlin, C. (2020, October 22). Plasmid Transfer by
Conjugation in Gram-Negative Bacteria: From the Cellular to the Community Level. NCBI.
Retrieved November 25, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7690428/