scholarly journals Facilitation of Robust Growth of Prochlorococcus Colonies and Dilute Liquid Cultures by “Helper” Heterotrophic Bacteria

2008 ◽  
Vol 74 (14) ◽  
pp. 4530-4534 ◽  
Author(s):  
J. Jeffrey Morris ◽  
Robin Kirkegaard ◽  
Martin J. Szul ◽  
Zackary I. Johnson ◽  
Erik R. Zinser
Keyword(s):  
Solid Medium ◽  
Heterotrophic Bacteria ◽  
Cell Concentration ◽  
Preliminary Evidence ◽  
Critical Threshold ◽  
Semisolid Medium ◽  
Marine Heterotrophic Bacteria ◽  
Pure Cultures ◽  
Novel Method ◽  
Axenic Cultures

ABSTRACT Axenic (pure) cultures of marine unicellular cyanobacteria of the Prochlorococcus genus grow efficiently only if the inoculation concentration is large; colonies form on semisolid medium at low efficiencies. In this work, we describe a novel method for growing Prochlorococcus colonies on semisolid agar that improves the level of recovery to approximately 100%. Prochlorococcus grows robustly at low cell concentrations, in liquid or on solid medium, when cocultured with marine heterotrophic bacteria. Once the Prochlorococcus cell concentration surpasses a critical threshold, the “helper” heterotrophs can be eliminated with antibiotics to produce axenic cultures. Our preliminary evidence suggests that one mechanism by which the heterotrophs help Prochlorococcus is the reduction of oxidative stress.

Novel Campylobacter Isolation Method Using Hydrophobic Grid Membrane Filter and Semisolid Medium†

2007 ◽  
Vol 70 (2) ◽  
pp. 355-362 ◽  
Author(s):  
ALFONSO VALDIVIESO-GARCIA ◽  
KATHLEEN HARRIS ◽  
EDWARD RICHE ◽  
STEPHANIE CAMPBELL ◽  
ANNE JARVIE ◽  
...  
Keyword(s):  
Membrane Filter ◽  
Simple Procedure ◽  
Meat Products ◽  
Variable Region ◽  
Initial Study ◽  
Epidemiological Studies ◽  
Campylobacter Coli ◽  
Semisolid Medium ◽  
Enrichment Broth ◽  
Pure Cultures

Culture procedures for isolation of thermophilic campylobacters from food matrices are complex, labor intensive, and time-consuming. Most available methods include the use of antibiotics as selective agents to prevent the growth of competing microflora. A simple procedure for isolation of thermophilic campylobacters after enrichment in Rosef's enrichment broth was developed using a hydrophobic grid membrane filter (HGMF) on semisolid medium (SSM). SSM contains no antibiotics, and the HGMF physically separates Campylobacter from the enrichment broth, allowing isolation based on differential motility. The HGMF-SSM method was compared to the Agriculture and Agri-Food Canada Food Safety Procedures Manual (FSPM-10) method (Isolation of Thermophilic Campylobacters from Fresh Pork, Beef, Veal, Poultry and Ready-to-Eat Meat Products), which includes the use of selective antibiotics. During the initial study, after enrichment the HGMF-SSM method yielded pure cultures of campylobacters after 16 to 18 h (overnight) compared with 48 h for the FSPM-10 method. Ninety-four turkey samples collected at local retail stores and 38 frozen pig fecal samples were processed by both methods. Thirty-five samples (26.5%) were positive by the HGMF-SSM method; 24 (18.2%) of these positive samples contained Campylobacter jejuni and 11 (8.3%) contained Campylobacter coli. With the FSPM-10 method, 25 samples (18.9%) were positive: 21 (15.9%) with C. jejuni and 4 (3%) with C. coli. For a subsequent field study, only the HGMF-SSM method was used to isolate Campylobacter from 1,200 chicken samples and 454 turkey samples sold at retail. Analysis of five subisolates from various samples indicated that only one type of Campylobacter was recovered by the HGMF-SSM method, as ascertained by MICs for 10 antimicrobials, sequencing of the short variable region of the flaA gene, and fingerprinting based on amplified fragment length polymorphism. The absence of antibiotics in the SSM may explain the higher recovery of thermophilic campylobacters. The HGMF-SSM method resulted in improved isolation of campylobacters and is simpler, faster, cheaper, and less labor intensive than the FSPM-10 method. The recovery of one type of Campylobacter from the chicken samples may have important implications, particularly in epidemiological studies.

scholarly journals Structure-Function Analysis Indicates that an Active-Site Water Molecule Participates in Dimethylsulfoniopropionate Cleavage by DddK

2019 ◽  
Vol 85 (8) ◽  
Author(s):  
Ming Peng ◽  
Xiu-Lan Chen ◽  
Dian Zhang ◽  
Xiu-Juan Wang ◽  
Ning Wang ◽  
...  
Keyword(s):  
Water Molecule ◽  
Active Site ◽  
Dimethyl Sulfide ◽  
Catalytic Mechanism ◽  
Heterotrophic Bacteria ◽  
Function Analysis ◽  
Cloud Condensation Nuclei ◽  
Oxidation Products ◽  
Condensation Nuclei ◽  
Marine Heterotrophic Bacteria

ABSTRACT The osmolyte dimethylsulfoniopropionate (DMSP) is produced in petagram quantities in marine environments and has important roles in global sulfur and carbon cycling. Many marine microorganisms catabolize DMSP via DMSP lyases, generating the climate-active gas dimethyl sulfide (DMS). DMS oxidation products participate in forming cloud condensation nuclei and, thus, may influence weather and climate. SAR11 bacteria are the most abundant marine heterotrophic bacteria; many of them contain the DMSP lyase DddK, and their dddK transcripts are relatively abundant in seawater. In a recently described catalytic mechanism for DddK, Tyr64 is predicted to act as the catalytic base initiating the β-elimination reaction of DMSP. Tyr64 was proposed to be deprotonated by coordination to the metal cofactor or its neighboring His96. To further probe this mechanism, we purified and characterized the DddK protein from Pelagibacter ubique strain HTCC1062 and determined the crystal structures of wild-type DddK and its Y64A and Y122A mutants (bearing a change of Y to A at position 64 or 122, respectively), where the Y122A mutant is complexed with DMSP. The structural and mutational analyses largely support the catalytic role of Tyr64, but not the method of its deprotonation. Our data indicate that an active water molecule in the active site of DddK plays an important role in the deprotonation of Tyr64 and that this is far more likely than coordination to the metal or His96. Sequence alignment and phylogenetic analysis suggest that the proposed catalytic mechanism of DddK has universal significance. Our results provide new mechanistic insights into DddK and enrich our understanding of DMS generation by SAR11 bacteria. IMPORTANCE The climate-active gas dimethyl sulfide (DMS) plays an important role in global sulfur cycling and atmospheric chemistry. DMS is mainly produced through the bacterial cleavage of marine dimethylsulfoniopropionate (DMSP). When released into the atmosphere from the oceans, DMS can be photochemically oxidized into DMSO or sulfate aerosols, which form cloud condensation nuclei that influence the reflectivity of clouds and, thereby, global temperature. SAR11 bacteria are the most abundant marine heterotrophic bacteria, and many of them contain DMSP lyase DddK to cleave DMSP, generating DMS. In this study, based on structural analyses and mutational assays, we revealed the catalytic mechanism of DddK, which has universal significance in SAR11 bacteria. This study provides new insights into the catalytic mechanism of DddK, leading to a better understanding of how SAR11 bacteria generate DMS.

scholarly journals Habitat and taxon as driving forces of carbohydrate catabolism in marine heterotrophic bacteria: example of the model algae-associated bacteriumZobellia galactanivoransDsijT

2016 ◽  
Vol 18 (12) ◽  
pp. 4610-4627 ◽  
Author(s):  
Tristan Barbeyron ◽  
François Thomas ◽  
Valérie Barbe ◽  
Hanno Teeling ◽  
Chantal Schenowitz ◽  
...  
Keyword(s):  
Heterotrophic Bacteria ◽  
Driving Forces ◽  
Marine Heterotrophic Bacteria ◽  
Carbohydrate Catabolism

scholarly journals Screening of a Soil Bacteria Collection for the Production of Alkali Thermostable Xylanases

2018 ◽  
Vol 10 (8) ◽  
pp. 232
Author(s):  
C. R. Sampaio ◽  
C. G. S. Silva ◽  
É. C. T. Anjos ◽  
R. P. M. Fernandes ◽  
M. F. Fernandes
Keyword(s):  
Selection Criteria ◽  
Soil Bacteria ◽  
Solid Medium ◽  
Xylanase Activity ◽  
Relative Activity ◽  
Optimum Activity ◽  
Ph Values ◽  
Xylan Hydrolysis ◽  
Pure Cultures ◽  
The Stability

This work aimed to evaluate a collection of common and rare soil bacteria regarding to extracellular xylanases production and to characterize the stability in contrasting conditions of temperature and pH of these enzymes. This collection consists of 120 isolates belonging to six phyla that were subjected to screening for xylanase activity in pure cultures and in the extracellular proteic extract (EPE). The ratio between the halos diameters of xylan hydrolysis and in the colonies on solid medium (ratio H:C) was used for the evaluation of cultures as selection criteria. EPEs of isolates with highest ratios H:C were evaluated for the specific xylanases activity at 50 °C for 1 h. EPE of the three isolates with the highest potential for activity under this condition were evaluated for optimum activity, stability at 60 °C and different pH values. Twenty-two isolates showed xylanase activity under these conditions. Xylanases from TC21 and TC119 showed high relative activity at temperatures up to 70 °C and were less sensitive to changes in pH. Soil bacteria show high potential as a source of extracellular xylanases adapted to extreme pH and temperature conditions, which are required in agroindustrial processes.

scholarly journals The Mannitol Utilization System of the Marine Bacterium Zobellia galactanivorans

2014 ◽  
Vol 81 (5) ◽  
pp. 1799-1812 ◽  
Author(s):  
Agnès Groisillier ◽  
Aurore Labourel ◽  
Gurvan Michel ◽  
Thierry Tonon
Keyword(s):  
Abc Transporter ◽  
Biochemical Characterization ◽  
Heterotrophic Bacteria ◽  
Dry Weight ◽  
Sole Source ◽  
Content Type ◽  
Wide Range ◽  
Marine Heterotrophic Bacteria ◽  
Operon Gene ◽  
Living Organisms

ABSTRACTMannitol is a polyol that occurs in a wide range of living organisms, where it fulfills different physiological roles. In particular, mannitol can account for as much as 20 to 30% of the dry weight of brown algae and is likely to be an important source of carbon for marine heterotrophic bacteria.Zobellia galactanivorans(Flavobacteriia) is a model for the study of pathways involved in the degradation of seaweed carbohydrates. Annotation of its genome revealed the presence of genes potentially involved in mannitol catabolism, and we describe here the biochemical characterization of a recombinant mannitol-2-dehydrogenase (M2DH) and a fructokinase (FK). Among the observations, the M2DH ofZ. galactanivoranswas active as a monomer, did not require metal ions for catalysis, and featured a narrow substrate specificity. The FK characterized was active on fructose and mannose in the presence of a monocation, preferentially K+. Furthermore, the genes coding for these two proteins were adjacent in the genome and were located directly downstream of three loci likely to encode an ATP binding cassette (ABC) transporter complex, suggesting organization into an operon. Gene expression analysis supported this hypothesis and showed the induction of these five genes after culture ofZ. galactanivoransin the presence of mannitol as the sole source of carbon. This operon for mannitol catabolism was identified in only 6 genomes ofFlavobacteriaceaeamong the 76 publicly available at the time of the analysis. It is not conserved in allBacteroidetes; some species contain a predicted mannitol permease instead of a putative ABC transporter complex upstream of M2DH and FK ortholog genes.

scholarly journals Metabolic strategies of sharing pioneer bacteria mediating fresh macroalgae breakdown

2021 ◽  
Author(s):  
Maéva Brunet ◽  
Nolwen Le Duff ◽  
Tristan Barbeyron ◽  
François Thomas
Keyword(s):  
Extracellular Enzymes ◽  
Heterotrophic Bacteria ◽  
Physical Contact ◽  
Brown Macroalgae ◽  
Resistance Proteins ◽  
Biomass Turnover ◽  
Macroalgal Biomass ◽  
Marine Heterotrophic Bacteria ◽  
Metabolic Strategies ◽  
Polysaccharide Utilization Loci

Macroalgae represent huge amounts of biomass worldwide, largely recycled by marine heterotrophic bacteria. We investigated the strategies of pioneer bacteria within the flavobacterial genus Zobellia to initiate the degradation of fresh brown macroalgae, which has received little attention compared to the degradation of isolated polysaccharides. Zobellia galactanivorans DsijT could use macroalgae as a sole carbon source and extensively degrade algal tissues without requiring physical contact, via the secretion of extracellular enzymes. This indicated a sharing behaviour, whereby pioneers release public goods that can fuel other bacteria. Comparisons of eight Zobellia strains, and strong transcriptomic shifts in Z. galactanivorans cells using fresh macroalgae vs. isolated polysaccharides, revealed potential overlooked traits of pioneer bacteria. Besides brown algal polysaccharide degradation, they notably include stress resistance proteins, type IX secretion system proteins and novel uncharacterized Polysaccharide Utilization Loci. Overall, this work highlights the relevance of studying fresh macroalga degradation to fully understand the niche, metabolism and evolution of pioneer degraders, as well as their cooperative interactions within microbial communities, as key players in macroalgal biomass turnover.

scholarly journals A newly isolated roseophage represents a distinct member of Siphoviridae family

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Lanlan Cai ◽  
Ruijie Ma ◽  
Hong Chen ◽  
Yunlan Yang ◽  
Nianzhi Jiao ◽  
...  
Keyword(s):  
Heterotrophic Bacteria ◽  
Phylogenetic Analyses ◽  
Gc Content ◽  
Genomic Analysis ◽  
Wide Distribution ◽  
Dinoroseobacter Shibae ◽  
Population Structures ◽  
Marine Heterotrophic Bacteria ◽  
Distinct Member ◽  
Biological Entities

Abstract Background Members of the Roseobacter lineage are a major group of marine heterotrophic bacteria because of their wide distribution, versatile lifestyles and important biogeochemical roles. Bacteriophages, the most abundant biological entities in the ocean, play important roles in shaping their hosts’ population structures and mediating genetic exchange between hosts. However, our knowledge of roseophages (bacteriophages that infect Roseobacter) is far behind that of their host counterparts, partly reflecting the need to isolate and analyze the phages associated with this ecologically important bacterial clade. Methods vB_DshS-R4C (R4C), a novel virulent roseophage that infects Dinoroseobacter shibae DFL12T, was isolated with the double-layer agar method. The phage morphology was visualized with transmission electron microscopy. We characterized R4C in-depth with a genomic analysis and investigated the distribution of the R4C genome in different environments with a metagenomic recruitment analysis. Results The double-stranded DNA genome of R4C consists of 36,291 bp with a high GC content of 66.75%. It has 49 genes with low DNA and protein homologies to those of other known phages. Morphological and phylogenetic analyses suggested that R4C is a novel member of the family Siphoviridae and is most closely related to phages in the genus Cronusvirus. However, unlike the Cronusvirus phages, R4C encodes an integrase, implying its ability to establish a lysogenic life cycle. A terminal analysis shows that, like that of λ phage, the R4C genome utilize the ‘cohesive ends’ DNA-packaging mechanism. Significantly, homologues of the R4C genes are more prevalent in coastal areas than in the open ocean. Conclusions Information about this newly discovered phage extends our understanding of bacteriophage diversity, evolution, and their roles in different environments.

The Filter-Feeding of Artemia

1963 ◽  
Vol 40 (1) ◽  
pp. 195-205
Author(s):  
M. R. REEVE
Keyword(s):  
Cell Size ◽  
Filtration Rate ◽  
Cell Concentration ◽  
Ingestion Rate ◽  
Plant Cells ◽  
A Value ◽  
Maximum Value ◽  
Pure Cultures ◽  
Constant Maximum ◽  
Maximum Ingestion Rate

1. The rates of filtration and of ingestion have been studied in Artemia of different ages feeding on pure cultures of plant cells of three different species, the concentrations of cells being varied over two orders of magnitude. 2. The animal is capable of regulating its rate of feeding in such a way that, as the cell concentration increases, the filtration rate maintains a constant maximum value while the ingestion rate increases. When the concentration reaches a value at which a constant maximum ingestion rate is attained, the filtration rate falls off. 3. In older animals the maximum ingestion rate is reached at a lower cell concentration than in younger animals. 4. The maximum filtration rate is independent of cell size. The maximum ingestion rate is inversely related to cell size, the total volume of cells ingested being the same for three species of plant cells. 5. The means whereby the animal maintains a maximum rate of total volume of cells ingested per unit time, irrespective of their size, has been investigated and is discussed.

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