Engineering a Culturable Serratia symbiotica Strain for Aphid Paratransgenesis
Aphids are global agricultural pests and important model organisms for studying bacterial symbiosis, but none of their native symbionts have been genetically manipulated to date. Elston et al. (e02245-20) characterized genetic tools and techniques that can be used to engineer a gut-associated symbiont, Serratia symbiotica CWBI-2.3T. A green fluorescent protein-tagged strain was used to study how rapidly this bacterium colonizes several aphid species and its effects on host fitness. This work serves as a foundation for understanding the evolution of this symbiont species and the development of symbiont-based techniques for studying and controlling aphids.
Environmental Conditions Modulate the Properties of Probiotic-Derived Extracellular Vesicles
Extracellular vesicles (EVs) are now recognized as ubiquitous mediators in intercellular communication and play an important role in host-microbe interactions. EVs derived from beneficial bacteria are regarded as promising tools for postbiotic applications. Rodovalho et al. previously reported the production of EVs with anti-inflammatory properties by the Gram-positive probiotic Propionibacterium freudenreichii. In this study (e02263-20), they show that biophysical features, protein content, and immunomodulatory effects of these EVs are shaped by the culture medium used to grow propionibacteria. Therefore, optimization of environmental and growth conditions was established as a tool to modulate the potential therapeutic applications of probiotic-derived EVs.
A Unique Fatty Acid-Recycling System Identified in Corynebacterium glutamicum
The industrial amino acid producer Corynebacterium glutamicum has evolved into a potential workhorse for fatty acid production. This organism naturally lacks the β-oxidative fatty acid degradation pathway; rather, Ikeda et al. (e02469-20) obtained evidence showing the presence of a unique mechanism of lipid homeostasis, namely, the formation of a futile cycle of acyl coenzyme A hydrolysis and resynthesis, presumably as a system for recycling excess fatty acids. This work further demonstrates that engineering of the cycle in a fatty acid producer leads to dramatically improved production.
In Vivo Assessments of Candidate Oral Probiotics To Prevent or Reduce Caries Risk
Dental caries remains a prevalent disease resulting from tooth demineralization by organic acids from fermented dietary carbohydrates by pathogens such as Streptococcus mutans. Culp et al. (e02490-20) describe in vivo assessments of oral commensal streptococci and isogenic mutants that, based on in vitro antagonism against S. mutans, are candidate anticaries probiotics. They identified strains that in competition with S. mutans enhanced colonization by autochthonous bacteria, plus a strain that under extreme cariogenic conditions was also competitive against S. mutans and decreased smooth-surface caries severity. This work establishes a valuable instrument for preclinical validation of oral probiotics against caries.
CRISPR Interference in the Lyme Disease Spirochete
Borrelia burgdorferi, a major vector-borne disease agent, has been difficult to study, in part because available genetic manipulation protocols are inefficient and slow. Takacs et al. (e02519-20) adapted a CRISPR interference method of gene product depletion for use in B. burgdorferi. The approach allows for rapid clone generation and highly (>95%) efficient depletion of transcripts of genes with broadly varied levels of native expression. To facilitate implementation, the CRISPR platform is available in five antibiotic resistance variations. The availability of this platform will facilitate genetic manipulation and characterization of an important human pathogen.
- Copyright © 2021 American Society for Microbiology.
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- Engineering a Culturable Serratia symbiotica Strain for Aphid Paratransgenesis
- Environmental Conditions Modulate the Properties of Probiotic-Derived Extracellular Vesicles
- A Unique Fatty Acid-Recycling System Identified in Corynebacterium glutamicum
- In Vivo Assessments of Candidate Oral Probiotics To Prevent or Reduce Caries Risk
- CRISPR Interference in the Lyme Disease Spirochete
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