Background
The genus Acinetobacter contains species that are capable of causing opportunistic hospital-acquired infections, with A.baumannii being the most clinically relevant. Of great concern is the high persistence of A.baumannii within the hospital setting due to resistance to disinfectants, prolonged survival on fomites and rapid emergence of multidrug resistance.

A number of pathogens appear to change their morphology in response to environmental stresses. Indeed, Acinetobacter undergoes reductive division, an increase in cell number without increasing biomass, in response to nutrient-limiting conditions, resulting in a transition to coccoid morphology. This morphological change has further been implied as important for the ability of Acineotbacter to adhere to surfaces to form aggregated biofilms, and in increased resistance to specific antimicrobials.

Aims
Prevention of colonisation and persistence of Acinetobacter in a healthcare setting is crucial, therefore a better understanding of the molecular mechanisms of survival under these nutrient-limited conditions could aid in eradication of Acinetobacter from hospitals. This study aims to identify genes important in reductive division and to investigate the regulation of elongation and division-specific growth during this morphological change.

Methods
Microscopy studies are currently being performed using functional fluorescent fusions of proteins involved in elongation and division-specific growth. Future studies will utilise mutant libraries to identify genes important for regulating cell morphology.

Results and Conclusion
Reductive division, and the associated coccoid morphology, under nutrient limitation has been observed in Acinetobacter species but not in E.coli, indicating species specificity. Co-localisation studies of the division-specific protein ZapA and the elongation-specific cytoskeletal protein MreB are currently being performed in Acinetobacter to investigate the role of these proteins during reductive division. An understanding of the molecular mechanisms involved in morphological changes in Acinetobacter and the role of such shape change in infection and survival may help in future control of this serious pathogen within hospitals.