The Complete Genome and Proteome of Laribacter hongkongensis Reveal Potential Mechanisms for Adaptations to Different Temperatures and Habitats

Abstract

Laribacter hongkongensis is a newly discovered Gram-negative bacillus of the Neisseriaceae family associated with freshwater fish–borne gastroenteritis and traveler's diarrhea. The complete genome sequence of L. hongkongensis HLHK9, recovered from an immunocompetent patient with severe gastroenteritis, consists of a 3,169-kb chromosome with G+C content of 62.35%. Genome analysis reveals different mechanisms potentially important for its adaptation to diverse habitats of human and freshwater fish intestines and freshwater environments. The gene contents support its phenotypic properties and suggest that amino acids and fatty acids can be used as carbon sources. The extensive variety of transporters, including multidrug efflux and heavy metal transporters as well as genes involved in chemotaxis, may enable L. hongkongensis to survive in different environmental niches. Genes encoding urease, bile salts efflux pump, adhesin, catalase, superoxide dismutase, and other putative virulence factors—such as hemolysins, RTX toxins, patatin-like proteins, phospholipase A1, and collagenases—are present. Proteomes of L. hongkongensis HLHK9 cultured at 37°C (human body temperature) and 20°C (freshwater habitat temperature) showed differential gene expression, including two homologous copies of argB, argB-20, and argB-37, which encode two isoenzymes of N-acetyl-L-glutamate kinase (NAGK)—NAGK-20 and NAGK-37—in the arginine biosynthesis pathway. NAGK-20 showed higher expression at 20°C, whereas NAGK-37 showed higher expression at 37°C. NAGK-20 also had a lower optimal temperature for enzymatic activities and was inhibited by arginine probably as negative-feedback control. Similar duplicated copies of argB are also observed in bacteria from hot springs such as Thermus thermophilus, Deinococcus geothermalis, Deinococcus radiodurans, and Roseiflexus castenholzii, suggesting that similar mechanisms for temperature adaptation may be employed by other bacteria. Genome and proteome analysis of L. hongkongensis revealed novel mechanisms for adaptations to survival at different temperatures and habitats.

Matrix-assisted laser desorption ionisation–time of flight mass spectrometry for rapid identification ofLaribacter hongkongensis

“…Laribacter hongkongensis is a Gram-negative, facultative anaerobic, motile, S-shaped, asaccharolytic, urease-positive bacillus that belongs to the Neisseriaceae family of β-proteobacteria 1. It was first isolated from the blood and thoracic empyema of an alcoholic liver cirrhosis patient in Hong Kong 2.…”

“…Although L hongkongensis is likely to be globally distributed, as travel histories from patients suggested its presence in at least four continents, most cases of L hongkongensis infections were reported in eastern countries 3 4 7 8 . L hongkongensis has been found in up to 60% of the intestines of commonly consumed freshwater fish of the carp family 1. It has also been isolated from drinking water reservoirs and Chinese tiger frogs in Hong Kong and little egrets in Hangzhou 1 9 10.…”

Novel Pan-Genomic Analysis Approach in Target Selection for Multiplex PCR Identification and Detection of Burkholderia pseudomallei, Burkholderia thailandensis, and Burkholderia cepacia Complex Species: a Proof-of-Concept Study

“…As with other virulent or emerging bacterial pathogens (34,45,51), complete genome sequences of 23 B. pseudomallei, four B. thailandensis, and 16 B. cepacia complex isolates have been made publicly available (http://www.ncbi.nlm.nih .gov/sites/genome). In the clinical microbiology setting, however, this information has yet to be fully exploited.…”

Automated Pangenomic Analysis in Target Selection for PCR Detection and Identification of Bacteria by Use of ssGeneFinder Webserver and Its Application to Salmonella enterica Serovar Typhi

“…They represent a wide diversity of clinically important bacteria, from wellknown virulent species such as Mycobacterium tuberculosis (5), Staphylococcus aureus (13) and Bacillus anthracis (21) to various pathogenic species that have been recognized or described only more recently (25,30). This wealth of information has major implications for the clinical microbiologist.…”