Farooq, N. | bioRxiv Science

bioRxiv2023

In vivo evolution of a Klebsiella pneumoniae capsule defect promotes complement-mediated opsono-phagocytosis and persistence during recurrent infection

Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) bloodstream infections rarely overwhelm the host but are associated with high mortality. The complement system is a key host defense against bloodstream infection. However, there are varying reports of serum resistance among KPC-Kp isolates. We assessed growth of 59 KPC-Kp clinical isolates in human serum and found increased resistance in 16/59 (27%). We identified five genetically-related bloodstream isolates with varying serum resistance profiles collected from a single patient during an extended hospitalization marked by recurrent KPC-Kp bloodstream infections. We noted a loss-of-function mutation in the capsule biosynthesis gene, wcaJ, that emerged during infection was associated with decreased polysaccharide capsule content, and resistance to complement-mediated killing. Surprisingly, disruption of wcaJ increased deposition of complement proteins on the microbial surface compared to the wild-type strain and led to increased complement-mediated opsono-phagocytosis in human whole blood. Disabling opsono-phagocytosis in the airspaces of mice impaired in vivo control of the wcaJ loss-of-function mutant in an acute lung infection model. These findings describe the rise of a capsular mutation that promotes KPC-Kp persistence within the host by enabling co-existence of increased bloodstream fitness and reduced tissue virulence. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/542722v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@155736eorg.highwire.dtl.DTLVardef@10d47c0org.highwire.dtl.DTLVardef@e1ab83org.highwire.dtl.DTLVardef@1c33131_HPS_FORMAT_FIGEXP M_FIG Graphical abstract Created with BioRender.com C_FIG

microbiology↗

bioRxiv2022

Coexistence between similar invaders: The case of two cosmopolitan exotic insects

Biological invasions are usually examined in the context of their impacts on native species. However, few studies have examined the dynamics between invaders when multiple exotic species successfully coexist in a novel environment. Yet, long-term coexistence of now established exotic species has been observed in North American lady beetle communities. Exotic lady beetles Harmonia axyridis and Coccinella septempunctata were introduced for biological control in agricultural systems and have since become dominant species within these communities. In this study, we investigated coexistence via spatial and temporal niche partitioning among H. axyridis and C. septempunctata using a 31-year dataset from southwestern Michigan, USA. We found evidence of long-term coexistence through a combination of small-scale environmental, habitat, and seasonal mechanisms. Across years, H. axyridis and C. septempunctata experienced patterns of cyclical dominance likely related to yearly variation in temperature and precipitation. Within years, populations of C. septempunctata peaked early in the growing season at 550 degree days, while H. axyridis populations grew in the season until 1250 degree days, and continued to have high activity after this point. Coccinella septempunctata was generally most abundant in herbaceous crops, whereas H. axyridis did not display strong habitat preferences. These findings suggest that within this region H. axyridis has broader habitat and abiotic environmental preferences, while C. septempunctata thrives under more specific ecological conditions. These ecological differences have contributed to the continued coexistence among these two invaders. Understanding mechanisms that allow coexistence of dominant exotic species contributes to native biodiversity conservation management of invaded ecosystems. Open research statementData are already published and publicly available, with those items properly cited in this submission. This submission uses novel code, which is provided, per our requirements, in an external repository to made available in perpetuity, and are available at https://github.com/ReproducibleQM/space_invader. Data sets utilized for this research (Landis 2020) are housed at EDI here: https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-kbs.23.30 (doi:10.6073/pasta/f0776c1574808b08c484c1f7645a7357). Weather data was downloaded directly from the Kellogg Biological Station data repository (https://lter.kbs.msu.edu/datatables/7) and downloading the full record. An archival record of these data are available at https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-kbs.2.107 (doi:10.6073/pasta/4c30523bae14c4340e4d9c90e72f90c4). Because both databases are living and subject to update as data is collected, databases as used within this study are mirrored within the code repository as CSV files.

ecology↗