New Discoveries in How Bacteria Grow: potential medical and environmental implications

New research, just published from a team based out of Indiana University, reveals a previously unidentified method in which bacteria grow and replicate.

For decades, rod-shaped bacteria like Escherichia coli (E. coli) and Bacillus subtilis have been thought to divide only by a method called "binary fission". Binary fission is a uniform elongation of the bacterial cell that ends with cleavage or division at the mid-point of the cell. The process creates two new symmetric cells.

New bacterial growth process called polar growth has been identified in a subset of rod-shaped bacteria. This method of growth and replication is very different than binary fission.

Polar growth refers to growth that occurs at a single end or pole of the bacterial cell.

Using the plant pathogen Agrobacterium tumefacien, scientists were able to label the cells in red and view them using time lapse microscopy to see where unlabeled new growth occurred. New growth was only observed at one end of the bacterium. The end containing new growth had all new proteins rather than an equal distribution of old and new proteins shared along the dividing bacterium.

The research was also extended to other related species within the class of Alphaproteobacteria. Polar growth was found in Sinorhizobium meliloti (a bacterial pathogen found in plants) and Brucella abortus and Ochrobactrum anthropil (two human pathogens).

It's been speculated that keeping older proteins and cell material in one cell and giving all new synthesized material to the new cell has genetic advantages to the long-term survival of the species.

Understanding the differences in how bacterial species grow and divide is important in a couple of different ways.

This new knowledge can be used to improve the methods used to grow of certain useful types of bacteria (e.g., bacteria used in oil spill remediation and eradicating disease-carrying mosquitoes).

This discovery will also aid in developing new antimicrobial methods.

Many bacterial species, like E. coli, can easily develop antibiotic resistance even with low level exposures to antibiotics. Bacterial genes and the subsequent protein products can evolve (change) rapidly in order to survive. This is how "superbugs" have become more common. Bacteria change leading to an evolution of antibiotic resistance - the bacteria are no longer resistant to common antibiotics.

Under selective pressures, rapid modification of antibiotic resistance genes and modification of the cell surface of bacteria can allow the species to evade detection by the host cell's defense mechanism and to survive antibiotic efforts - resulting in a superbug that can proliferate.

An increasing number of bacterial species are becoming resistant to all known antibiotics - a phenomenon known as "multi-resistance". It's considered one of the most significant emerging threats to public health.

Understanding how bacteria replicate will provide new insights on how to combat this ongoing problem.

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