Dr Kayley Usher, from the CSIRO, was our guest speaker for the October meeting and presented a talk entitled ‘How marvellous microbes made our world’.
We were introduced into the world of the microscopic and sub-microscopic through a series of images and were presented with some interesting aspects of microbial life and its activities.
A group term for a range of ultra-small life forms is microbes and includes: Archaea, Eucarya, Fungi and bacteria. Some important characteristics between these domains were explained, some of the extreme conditions in which they can exist and a few examples of specialised forms of bacteria were introduced. Not all microbes are single cells but they can function as complex pro organelles with specialised existences. An interesting example is magnetosomes that contain magnetic crystals and have flagella that enable them to source their food magnetically.
We were reminded of the great antiquity of bacterial activities and that thrombolites and stromatolites were developing about 3.5 billion years ago. These fossilised layered accumulations of calcareous sediment were formed by the activities of colonies of bacteria and resulted in the first life forms on Earth. Micro-organisms were to remain the only life forms in the Archean history of the Earth.
The study of micro-organisms requires different types of microscope and high tech equipment; these include microscopes with fluorescence attachments using light sources, the transmitting electron microscope (TEM) and the scanning electron microscope (SEM). The energy sources used in both TEM and SEM are electron beams and this enables details to single wave length dimensions to be examined. Both TEM and SEM equipment is based at the Centre for Microscopy and Microanalysis at UWA, and are used by researchers from many Institutions on an hourly basis.
The images used for the talk were largely those produced by TEM and SEM microscopy and we were shown a fascinating selection illustrating the varied forms of several bacteria including coccoid, spiral, flagellated and rod-like forms as well as examples that were attached to one another and to the substrate via a series of microfilaments. Electricity is conducted through this nano wiring system allowing the bacterial colony to communicate. Microbes tend to live in communities, acting together symbiotically. They co-operate through biofilms where they attach to the surfaces, grow and then detach to recolonise. Bacteria also communicate as colonies using chemical sensing, termed quorum sensing. Bacteria can also sense smells and head for food!
Microbial environments are everywhere. As examples, extremophiles dwell in environments that are; highly saline, high temperature, extreme pH, with toxic metals, at depths of 1.6 km in sediments and they do not require organic carbon to exist. The first mass extinction was likely caused by the activities of cyanobacteria in the Archean when large amounts of free oxygen was being produced as a by-product of iron precipitation. The importance and significance of microbial life become apparent when considering such examples as mycorrhiza activity (symbiotic relationship between a fungus and a plant) that benefits plants by an increase the water and mineral take up capacity and nitrogen-fixing bacteria that improve soil fertility. As humans the abundance of micro-organisms is considerable when we learn that our cells are 99% comprised of microbial life. Microbes manufacture the vitamin K in our bodies and aid digestion processes. Cell mitochondria are a specialised form of bacteria.
Kayley’s particular area of research includes interactions between natural metal ores and bacteria. Her work has shown that elemental metal can be released from mineral ores by bacterial chemical processes such as isolating copper from copper sulphide ore. Element mapping using TEM showed the distribution of certain elements within the bacteria as chemical changes progressed.
We were introduced to the mechanisms of rusting on metals with an explanation about rusticles and their development. Images of the wreck of the Titanic over a number of years show how rusticles (pendulous growths of rusting iron) have enlarged as corrosion has advanced. Eventually all materials, including concrete, wood, metals and plastics, become degraded by microbial action.
There are many positive ways that microbes can be utilised including the cleaning up of toxic waste and degradation of contaminants such as oil spills. In outlining a few of the important aspects of microbial activity Kayley made us aware of some important research work and its potential applications.
Susan Stocklmayer