Phylogenetic mapping of bacterial morphology

Area of Science:

• Microbial Evolution
• Bacterial Phylogenetics
• Cell Morphology

Background:

• Molecular phylogenies provide a framework for understanding bacterial evolution.
• Classical morphological descriptions are often used in bacterial classification.
• The relationship between bacterial morphology and evolutionary history requires further investigation.

Purpose of the Study:

• To map bacterial morphologies onto molecular phylogenies.
• To investigate the evolutionary origins and persistence of bacterial shapes.
• To explore the role of peptidoglycan in bacterial body plan evolution.

Main Methods:

• Comparative analysis of small-subunit ribosomal RNA (rRNA) sequences to establish bacterial phylogeny.
• Mapping classical morphological descriptions onto the deduced phylogenetic tree.
• Review of experimental evidence for morphogenesis and microbial fossil records.

Main Results:

• Bacterial coccus shape has evolved independently multiple times in separate lineages.
• Other morphologies have evolved only once.
• Bacterial morphology is consistent with molecular phylogeny, though not useful for defining it.
• Experimental and fossil evidence corroborate these findings.

Conclusions:

• Bacterial morphology, particularly cell shape, is a reliable indicator of evolutionary history once phylogeny is established.
• The biophysical properties of peptidoglycan and genetic control likely drive the accumulation of persistent morphologies.
• An evolved body plan based on peptidoglycan may have been a critical step in bacterial evolution.
• Integrating biological data with phylogenetic structure yields significant evolutionary insights.