Pseudoalteromonas

Aims:  The goal of this study was to identify a marine algae-associated bacterium isolated from Laminaria japonica and investigate this microorganism's growth-promoting effects on plants.Methods and Results:  The bacterium, identified as Pseudoalteromonas porphyrae, was determined to display a biostimulatory activity for seed germination and shoot growth in several agricultural plants and also for growth in ginseng callus cell culture. This biostimulatory activity was linked to a catalase enzyme that was excreted in the maximal amount during the transition from logarithmic growth phase to stationary growth phase. In addition, selected shifts in growth temperature and medium salinity affected the amount of enzyme excreted. The purified catalase was determined to be composed of identical subunits. The catalase of interest displayed significantly higher biostimulatory activity than the catalase from bovine liver.Conclusions:  The catalase investigated in this study is unique in that it promotes growth in and possibly contributes to stress tolerance of plants.Significance and Impact of the Study:  The catalase of interest has the potential for use in treatments that aim to improve percent seed germination as well as obtaining tall shoots in a shorter time period.

Complex hydrocarbon and aromatic compounds degrading marine bacterial strains were isolated from deep sea sediment after enrichment on spent engine (SE) oil. Phenotypic characterization and phylogenetic analysis of 16S rRNA gene sequences showed the isolates were related to members of the Pseudoalteromonas sp., Ruegeria sp., Exiguobacterium sp. and Acinetobacter sp. Biodegradation using 1% (v/v) SE oil with individual and mixed strains showed the efficacy of SE oil utilization within a short retention time. The addition of non-ionic surfactant 0.05% (v/v) Tween 80 as emulsifying agent enhanced the solubility of hydrocarbons and renders them more accessible for biodegradation. The degradation of several compounds and the metabolites formed during the microbial oxidation process were confirmed by Fourier transform infrared spectroscopy and Gas chromatography-mass spectrometry analyses. The potential of this consortium to biodegrade SE oil with and without emulsifying agent provides po...

A total of five highly related strains of an unidentified marine bacterium were analyzed through their short genome sequences (AM260709–AM260713). Genome-to-Genome Distance (GGDC) showed high similarity to Pseudoalteromonas haloplanktis (X67024). The generated unique Quick Response (QR) codes indicated no identity to other microbial species or gene sequences. Chaos Game Representation (CGR) showed the number of bases concentrated in the area. Guanine residues were highest in number followed by cytosine. Frequency of Chaos Game Representation (FCGR) indicated that CC and GG blocks have higher frequency in the sequence from the evaluated marine bacterium strains. Maximum GC content for the marine bacterium strains ranged 53-54%. The use of QR codes, CGR, FCGR, and GC dataset helped in identifying and interpreting short genome sequences from specific isolates. A phylogenetic tree was constructed with the bootstrap test (1000 replicates) using MEGA6 software. Principal Component Analysi...

Aims:  To assess the diversity of antibiotic-resistant bacteria and their resistance genes in typical maricultural environments.Methods and Results:  Multidrug-resistant bacteria and resistance genes from a mariculture farm of China were analysed via cultivation and polymerase chain reaction (PCR) methods. Oxytetracycline (OTC)-resistant bacteria were abundant in both abalone and turbot rearing waters, accounting for 3·7% and 9·9% of the culturable microbes. Multidrug resistance was common, with simultaneous resistance to OTC, chloramphenicol and ampicillin the most common resistance phenotype. 16S rDNA sequence analyses indicate that the typical resistant isolates belonged to marine Vibrio, Pseudoalteromonas or Alteromonas species, with resistance most common in Vibrio splendidus isolates. For OTC resistance, tet(A), tet(B) and tet(M) genes were detected in some multidrug-resistant isolates, with tet(D) being the most common molecular determinant. For chloramphenicol resistance, cat II was common, and floR was also detected, especially in marine Pseudoalteromonas strains.Conclusions:  There is the risk of multidrug-resistant bacteria contamination in mariculture environments and marine Vibrio and Pseudoalteromonas species serve as reservoirs of specific antibiotic resistance determinants.Significance and Impact of the Study:  This paper and similar findings from Korea and Japan indicate the potential for widespread distribution of antibiotic resistance genes in mariculture environments from the East Asian region of the world.

The cold-adapted α-amylase from Pseudoalteromonas haloplanktis (AHA) is a multidomain enzyme capable of reversible unfolding. Cold-adapted proteins, including AHA, have been predicted to be structurally flexible and conformationally unstable as a consequence of a high lysine-to-arginine ratio. In order to examine the role of low arginine content in structural flexibility of AHA, the amino groups of lysine were guanidinated to form homo-arginine (hR), and the structure–function–stability properties of the modified enzyme were analyzed by transverse urea gradient-gel electrophoresis. The extent of modification was monitored by MALDI-TOF-MS, and correlated to changes in activity and stability. Modifying lysine to hR produced a conformationally more stable and less active α-amylase. The kcat of the modified enzyme decreased with a concomitant increase in ΔH# and decrease in Km. To interpret the structural basis of the kinetic and thermodynamic properties, the hR residues were modeled in the AHA X-ray structure and compared to the X-ray structure of a thermostable homolog. The experimental properties of the modified AHA were consistent with K106hR forming an intra-Domain B salt bridge to stabilize the active site and decrease the cooperativity of unfolding. Homo-Arg modification also appeared to alter Ca2+ and Cl− binding in the active site. Our results indicate that replacing lysine with hR generates mesophilic-like characteristics in AHA, and provides support for the importance of lysine residues in promoting enzyme cold adaptation. These data were consistent with computational analyses that show that AHA possesses a compositional bias that favors decreased conformational stability and increased flexibility. Proteins 2006. © 2006 Wiley-Liss, Inc.

Background: Marine bacteria of the genus Pseudoalteromonas are recognized as major producers of various biologically active metabolites of relevant clinical interest, some of which include halogenated compounds, cyclic peptides, toxic proteins, enzymes or exopolymer polyanionic substances, among others. Furthermore, the extracellular proteins of Pseudoalteromonas have been reported to contain both hydrolytic and antibiotic activities. In previous studies, we isolated a protein with a molecular mass of 80 kDa from Pseudoalteromonas sp., with showed antimicrobial activity against S. aureus MRSA, E. coli and multiresistant P. aeruginosa. In this context, it became important elucidate the mechanisms of action by which antimicrobial compounds affect certain molecular targets to inhibit bacterial growth or to cause death. In this work, we studied whether the antimicrobial protein of Pseudoalteromonas sp. is linked to hydrolytic activity when tested on a strain of methicillin-resistant Staphylococcus aureus. Methods: The antimicrobial protein was purified by molecular exclusion and ion exchange chromatography and its antimicrobial activity was tested by the disk diffusion method. Caseinolytic activity was measured by the method of Kunitz in the presence or absence of inhibitors. We observed that the protein lost activity in the presence of serine protease inhibitors. However, the presence or absence of inhibitors did not affect its antimicrobial activity.  Conclusion: The antimicrobial activity of this protein from Pseudoalteromonas sp. showed proteolytic activity. However, this activity was not responsible for its antimicrobial activity.

The psychrotolerant strain Pseudoalteromonas antarctica NF3, a Gram-negative bacterium isolated from muddy soil samples of Antarctica, secretes large amounts of a mucoid exopolymer with a high protein content. It has self-assembly properties and capacity to coat and protect liposomes against surfactants. We examined the ultrastructure of P. antarctica and the extracellular matter it secretes by transmission electron microscopy (TEM) after high-pressure freezing, freeze substitution (HPF-FS), and Epon embedding, and compared this with information obtained by conventional methods. The improvements brought about by HPF-FS to the ultrastructural preservation of the extracellular matter allowed us to establish for the first time, in P. antarctica NF3, the presence of two components: a large amount of cell-derived outer membrane vesicles containing proteins and a capsular polymer around the cells.

Bacteria belonging to the Burkholderia cepacia complex (Bcc) are significant pathogens in Cystic Fibrosis (CF) patients and are resistant to a plethora of antibiotics. In this context, microorganisms from Antarctica are interesting because they produce antimicrobial compounds inhibiting the growth of other bacteria. This is particularly true for bacteria isolated from Antarctic sponges. The aim of this work was to characterize a set of Antarctic bacteria for their ability to produce new natural drugs that could be exploited in the control of infections in CF patients by Bcc bacteria. Hence, 11 bacterial strains allocated to different genera (e.g., Pseudoalteromonas, Arthrobacter and Psychrobacter) were tested for their ability to inhibit the growth of 21 Bcc strains and some other human pathogens. All these bacteria completely inhibited the growth of most, if not all, Bcc strains, suggesting a highly specific activity toward Bcc strains. Experimental evidences showed that the antimicrobial compounds are small volatile organic compounds, and are constitutively produced via an unknown pathway. The microbial volatile profile was obtained by SPME-GC-MS within the m/z interval of 40-450. Solid phase micro extraction technique affords the possibility to extract the volatile compounds in head space with a minimal sample perturbation. Principal component analysis and successive cluster discriminant analysis was applied to evaluate the relationships among the volatile organic compounds with the aim of classifying the microorganisms by their volatile profile. These data highlight the potentiality of Antarctic bacteria as novel sources of antibacterial substances to face Bcc infections in CF patients.

Pseudoalteromonas is a genus of ubiquitous marine bacteria used as model organisms to study the biological mechanisms involved in the adaptation to cold conditions. A remarkable feature shared by these bacteria is their ability to produce secondary metabolites with a strong antimicrobial and antitumor activity. Despite their biotechnological relevance, representatives of this genus are still lacking (with few exceptions) an extensive genomic characterization, including features involved in the evolution of secondary metabolites production. Indeed, biotechnological applications would greatly benefit from such analysis. Here, we analyzed the genomes of 38 strains belonging to different Pseudoalteromonas species and isolated from diverse ecological niches, including extreme ones (i.e. Antarctica). These sequences were used to reconstruct the largest Pseudoalteromonas pangenome computed so far, including also the two main groups of Pseudoalteromonas strains (pigmented and not pigmented ...