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ITQB NOVA researchers challenge a 50-year-old assumption on the division of Staphylococcus aureus

Multi-drug resistant Staphylococcus aureus – also known as MRSA – is a major cause of hospital-acquired infections, as well as infections in the community setting that are becoming increasingly difficult to treat. Developing new antibiotics may not always be the answer, and alternative strategies may prove both cheaper and more efficient. At ITQB NOVA, a team led by Mariana Gomes Pinho, and supported by an ERC Consolidator grant, dedicates their research to exploring the cell cycle and finding specific stages in which the bacteria might be more vulnerable.

The team’s most recent finding was published today in Nature Communications, and challenges a five-decade-long assumption. Since the 1970s, Staphylococcus aureus was thought to divide into three alternating perpendicular planes over three consecutive division cycles. In this new work, the Bacterial Cell Biology Lab shows, for three different strains, that S. aureus cells do not regularly divide into three alternating perpendicular planes. Imaging of the divisome showed that a plane of division is always perpendicular to the previous one, avoiding bisection of the nucleoid, which segregates along an axis parallel to the closing septum. However, one out of the multiple planes perpendicular to the septum which divide the cell into two identical halves can be used in daughter cells, irrespective of its orientation in relation to the penultimate division plane. Therefore, division in three orthogonal planes is not the rule in S. aureus (see video for an animation of three consecutive division cycles).

The evolution of the available technology was key to this finding. In the 1970s, the mode of division in alternating perpendicular planes was proposed based on light microscopy images of individual S. aureus cells embedded in soft agar undergoing three consecutive divisions or on scanning electron microscopy images of cubic packages of S. aureus cells grown in conditions that impair cell separation. In the current work, super-resolution fluorescence microscopy showed that, although a plane of division is always perpendicular to the previous one, it is not necessarily perpendicular to the penultimate division plane. As a consequence, the majority of S. aureus cells do not divide into three alternating orthogonal planes.

Original Paper

Nature Communications |

Reassessment of the distinctive geometry of Staphylococcus aureus cell division

Bruno M. Saraiva, Moritz Sorg, Ana R. Pereira, Mário J. Ferreira, Léo C. Caulat, Nathalie T. Reichmann & Mariana G. Pinho 

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