Marine phytoplankton blooms are annual spring events that sustain active and diverse bloom-associated bacterial populations. Blooms vary considerably in terms of eukaryotic species composition and environmental conditions, but a limited number of heterotrophic bacterial lineages - primarily members of the Flavobacteriia, Alphaproteobacteria and Gammaproteobacteria - dominate these communities. In this Review, we discuss the central role that these bacteria have in transforming phytoplankton-derived organic matter and thus in biogeochemical nutrient cycling. On the basis of selected field and laboratory-based studies of flavobacteria and roseobacters, distinct metabolic strategies are emerging for these archetypal phytoplankton-associated taxa, which provide insights into the underlying mechanisms that dictate their behaviours during blooms.

An atypically large outbreak of Elizabethkingia anophelis infections occurred in Wisconsin. Here we show that it was caused by a single strain with thirteen characteristic genomic regions. Strikingly, the outbreak isolates show an accelerated evolutionary rate and an atypical mutational spectrum. Six phylogenetic sub-clusters with distinctive temporal and geographic dynamics are revealed, and their last common ancestor existed approximately one year before the first recognized human infection. Unlike other E. anophelis, the outbreak strain had a disrupted DNA repair mutY gene caused by insertion of an integrative and conjugative element. This genomic change probably contributed to the high evolutionary rate of the outbreak strain and may have increased its adaptability, as many mutations in protein-coding genes occurred during the outbreak. This unique discovery of an outbreak caused by a naturally occurring mutator bacterial pathogen provides a dramatic example of the potential impact of pathogen evolutionary dynamics on infectious disease epidemiology.

ABSTRACTMembers of theRoseobacterlineage of marine bacteria are prolific surface colonizers in marine coastal environments, and antimicrobial secondary metabolite production has been hypothesized to provide a competitive advantage to colonizing roseobacters. Here, we report that the roseobacterPhaeobactersp. strain Y4I produces the blue pigment indigoidine via a nonribosomal peptide synthase (NRPS)-based biosynthetic pathway encoded by a novel series of genetically linked genes:igiBCDFE. A Tn5-based random mutagenesis library of Y4I showed a perfect correlation between indigoidine production by thePhaeobacterstrain and inhibition ofVibrio fischerion agar plates, revealing a previously unrecognized bioactivity of this molecule. In addition, igiD null mutants (igiD encoding the indigoidine NRPS) were more resistant to hydrogen peroxide, less motile, and faster to colonize an artificial surface than the wild-type strain. Collectively, these data provide evidence for pleiotropic effects of indigoidine production in this strain. Gene expression assays support phenotypic observations and demonstrate thatigiDgene expression is upregulated during growth on surfaces. Furthermore, competitive cocultures ofV. fischeriand Y4I show that the production of indigoidine by Y4I significantly inhibits colonization ofV. fischerion surfaces. This study is the first to characterize a secondary metabolite produced by an NRPS in roseobacters.

The genus Chryseobacterium in the family Weeksellaceae is known to be polyphyletic. Amino acid identity (AAI) values were calculated from whole-genome sequences of species of the genus Chryseobacterium, and their distribution was found to be multi-modal. These naturally-occurring non-continuities were leveraged to standardise genus assignment of these species. We speculate that this multi-modal distribution is a consequence of loss of biodiversity during major extinction events, leading to the concept that a bacterial genus corresponds to a set of species that diversified since the Permian extinction. Transfer of nine species ( Chryseobacterium arachidiradicis , Chryseobacterium bovis , Chryseobacterium caeni , Chryseobacterium hispanicum , Chryseobacterium hominis , Chryseobacterium hungaricum , Chryseobacterium molle , Chryseobacterium pallidum and Chryseobacterium zeae ) to the genus Epilithonimonas and eleven ( Chryseobacterium anthropi , Chryseobacterium antarcticum , Chryseobacterium carnis , Chryseobacterium chaponense , Chryseobacterium haifense, Chryseobacterium jeonii, Chryseobacterium montanum , Chryseobacterium palustre , Chryseobacterium solincola , Chryseobacterium treverense and Chryseobacterium yonginense ) to the genus Kaistella is proposed. Two novel species are described: Kaistella daneshvariae sp. nov. and Epilithonimonas vandammei sp. nov. Evidence is presented to support the assignment of Planobacterium taklimakanense to a genus apart from Chryseobacterium, to which Planobacterium salipaludis comb nov. also belongs. The novel genus Halpernia is proposed, to contain the type species Halpernia frigidisoli comb. nov., along with Halpernia humi comb. nov., and Halpernia marina comb. nov.

The genus Elizabethkingia is genetically heterogeneous, and the phenotypic similarities between recognized species pose challenges in correct identification of clinically derived isolates. In addition to the type species Elizabethkingia meningoseptica, and more recently proposed Elizabethkingia miricola, Elizabethkingia anophelis and Elizabethkingia endophytica, four genomospecies have long been recognized. By comparing historic DNA-DNA hybridization results with whole genome sequences, optical maps, and MALDI-TOF mass spectra on a large and diverse set of strains, we propose a comprehensive taxonomic revision of this genus. Genomospecies 1 and 2 contain the type strains E. anophelis and E. miricola, respectively. Genomospecies 3 and 4 are herein proposed as novel species named as Elizabethkingia bruuniana sp. nov. (type strain, G0146 = DSM 2975 = CCUG 69503 = CIP 111191) and Elizabethkingia ursingii sp. nov. (type strain, G4122 = DSM 2974 = CCUG 69496 = CIP 111192), respectively. Finally, the new species Elizabethkingia occulta sp. nov. (type strain G4070 = DSM 2976 = CCUG 69505 = CIP 111193), is proposed.