Endosymbiont dominated bacterial communities in a dwarf spider

Area of Science:

• Microbiology
• Arachnology
• Genomics

Background:

• Spider microbial communities are poorly understood.
• Previous studies focused on pathogenic bacteria and known endosymbionts using limited screening methods.
• This limited scope hampered the detection of novel bacterial species in spiders.

Purpose of the Study:

• To comprehensively characterize the bacterial species within the dwarf spider Oedothorax gibbosus.
• To identify previously unreported endosymbiont bacteria in spiders.
• To investigate the overall bacterial community structure in spiders.

Main Methods:

• Utilized a combination of cloning assays, Denaturing Gradient Gel Electrophoresis (DGGE) profiling, and high-throughput sequencing.
• Analyzed multiple individuals of the dwarf spider Oedothorax gibbosus.
• Sequenced approximately 4.5 million reads to identify bacterial species.

Main Results:

• Detected a co-infection of known endosymbionts (Wolbachia, Rickettsia, Cardinium) and a novel endosymbiont, Rhabdochlamydia, in Oedothorax gibbosus.
• Rhabdochlamydia sequences closely matched R. porcellionis (woodlouse pathogen) and R. crassificans (cockroach endosymbiont).
• Observed high abundance of Rhabdochlamydia in one population, particularly in females, and Acinetobacter in one individual. Over 99% of reads belonged to five bacterial species.

Conclusions:

• The bacterial communities in Oedothorax gibbosus are dominated by endosymbiont bacteria, challenging previous findings in terrestrial arthropods.
• The newly identified Rhabdochlamydia and other endosymbionts suggest a specialized microbial association in this spider species.
• This endosymbiont-dominated bacterial community pattern may be prevalent across the Araneae order.