The life cycle of microbes

How do viruses develop?

Viruses are a type of parasite – they can’t live and replicate independently. When a virus infects a microbe, it injects its DNA into the cell. The DNA acts as a recipe book or set of instructions to make all the parts needed for new viruses. The virus often hijacks the cell’s replication machinery for its use. Inside the cell, viruses build lots of new copies of themselves. When they are ready, the virus bursts the cell like a balloon, releasing all the new viruses into the environment where they can search for new cells to infect. Whole populations of microbes can soon be infected in this way.

Do microbes die?

Microbes, like bacteria and fungi, die just like plants and animals. Even viruses, which are not living organisms but infectious agents, deteriorate so they are no longer functional and therefore not able to infect living cells. However, microbes are very resilient and can survive for a long period in conditions that plants and animals would struggle to survive. For example, some microbes can lie dormant in protective spores and survive for long periods, and then start growing again when provided with conditions that help them wake up and grow. Scientists have been able to revive microbes that are thought to have been trapped in salt crystals for 250 million years. Despite their toughness, it is possible to kill microbes under certain conditions such as with heat or chemicals. That’s why we use soap to wash our hands and to help get rid of harmful microbes.

Can a virus attach to another microbe?

On the surface of a virus, there’s often a structure that works like a “key”. Viruses infect microbes by bumping into them and then seeing whether their key recognises a “lock” to open a door into the cell. The locks are often found on structures on the cell surface, such as pili (long hairs) or flagella (whip-like structures that help the microbe to move). If a virus doesn’t have the right key, or if the cell has no locks, then the virus can’t infect the cell. For this reason, viruses are often quite specific for a single type of microbe. Cells can also hide the locks on their surface to stop viruses from infecting them, but this often comes at a cost to the microbe.

Why do damaging viruses appear every 100 years?

The idea that damaging virus appear every 100 years probably comes from the history of pandemics that had a major impact on humans; COVID-19 appeared in 2020, and Spanish flu appeared in 1918 and caused a devastating a pandemic 100 years before that. However, perception of a 100-year cycle may be a simplification rather than a precise scientific pattern. Viruses are constantly evolving and generating new strains which go on to cause large numbers of disease in the human population. Whether or not these turn into damaging pandemics determined by other factors in the human population that affect vulnerability to infection the ability of the virus to spread. This is why scientists work hard to understand these viruses and develop surveillance systems and vaccines to help protect us and reduce the threat of future pandemics.