Omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) provide significant health benefits and this has led to an increased consumption as dietary supplements. Omega-3 fatty acids EPA and DHA are found in animals, transgenic plants, fungi and many microorganisms but are typically extracted from fatty fish, putting additional pressures on global fish stocks. As primary producers, many marine microalgae are rich in EPA (C20:5) and DHA (C22:6) and present a promising source of omega-3 fatty acids. Several heterotrophic microalgae have been used as biofactories for omega-3 fatty acids commercially, but a strong interest in autotrophic microalgae has emerged in recent years as microalgae are being developed as biofuel crops. This paper provides an overview of microalgal biotechnology and production platforms for the development of omega-3 fatty acids EPA and DHA. It refers to implications in current biotechnological uses of microalgae as aquaculture feed and future biofuel crops and explores potential applications of metabolic engineering and selective breeding to accumulate large amounts of omega-3 fatty acids in autotrophic microalgae.

https://researchonline.jcu.edu.au/28112/1/Microalgal_biofactories_a_promising_approach.pdf

Microalgal biofactories: a promising approach towards sustainable omega-3 fatty acid production

The intensive rearing of various fish species in aquaculture has revealed intimate relationships between fish and bacteria that eventually may affect establishment of a ``normal'' mucosal microflora or result in disease epizootics. Interactions between bacteria and mucosal surfaces play important roles both at the egg and larval stages of marine fish. Bacterial adhesion and colonization of the egg surface occur within hours after fertilization. The diverse flora which eventually develops on the egg appears to reflect the bacterial composition and load of the ambient water, but species-specific adhesion at the egg surface may also play a role in development of the egg epiflora. Proteolytic enzymes produced by members of the adherent epiflora may cause serious damage to the developing egg and may also affect further adhesion of the epiflora. Ingestion of bacteria at the yolk sac stage results in establishment of a primary intestinal microflora which seems to persist beyond first feeding. Establishment of a gut microflora is likely to undergo several stages, resulting in an ``adult'' microflora weeks to months after first feeding. Ingested bacteria may serve as an exogenous supply of nutrients or essential factors at an early life stage. Early exposure to high bacterial densities is probably important for immune tolerance, and thus for the establishment of a protective intestinal microflora. Successful rearing of early life stages of several marine fish species depends on knowledge of the complex interactions among the cultured organisms and the bacterial communities which develop at the mucosal surfaces and in the ambient water and rearing systems. The routine use of antibiotics during rearing of fish larvae is not advisable, since it may increase the risk of promoting antibiotic resistance and adversely affect the indigenous microflora of the larvae. The use of probiotics has proven advantageous in domestic animal production, and the search for effective probiotics may have a great potential in aquaculture of marine organisms. Bacteria with antagonistic effects against fish pathogens have been successfully administered to several fish species, resulting in decreased mortality or increased growth rate.

Bacterial Interactions in Early Life Stages of Marine Cold Water Fish.

Plasmids encode partitioning genes (par) that are required for faithful plasmid segregation at cell division. Initially, par loci were identified on plasmids, but more recently they were also found on bacterial chromosomes. We present here a phylogenetic analysis of par loci from plasmids and chromosomes from prokaryotic organisms. All known plasmid-encoded par loci specify three components: a cis-acting centromere-like site and two trans-acting proteins that form a nucleoprotein complex at the centromere (i.e. the partition complex). The proteins are encoded by two genes in an operon that is autoregulated by the par-encoded proteins. In all cases, the upstream gene encodes an ATPase that is essential for partitioning. Recent cytological analyses indicate that the ATPases function as adaptors between a host-encoded component and the partition complex and thereby tether plasmids and chromosomal origin regions to specific subcellular sites (i.e. the poles or quarter-cell positions). Two types of partitioning ATPases are known: the Walker-type ATPases encoded by the par/sop gene family (type I partitioning loci) and the actin-like ATPase encoded by the par locus of plasmid R1 (type II partitioning locus). A phylogenetic analysis of the large family of Walker type of partitioning ATPases yielded a surprising pattern: most of the plasmid-encoded ATPases clustered into distinct subgroups. Surprisingly, however, the par loci encoding these distinct subgroups have different genetic organizations and thus divide the type I loci into types Ia and Ib. A second surprise was that almost all chromosome-encoded ATPases, including members from both Gram-negative and Gram-positive Bacteria and Archaea, clustered into one distinct subgroup. The phylogenetic tree is consistent with lateral gene transfer between Bacteria and Archaea. Using database mining with the ParM ATPase of plasmid R1, we identified a new par gene family from enteric bacteria. These type II loci, which encode ATPases of the actin type, have a genetic organization similar to that of type Ib loci.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2958.2000.01975.x

Plasmid and chromosome partitioning: surprises from phylogeny.

http://www.dzumenvis.nic.in/Biodegradation/pdf/Interactions%20between%20fish%20larvae.pdf

Interactions between fish larvae and bacteria in marine aquaculture

Disclosed is a process for growing the microflora Thraustochytrium, Schizochytrium and mixtures thereof, which includes the growing of the microflora in fermentation medium containing non-chloride containing sodium salts, in particular sodium sulfate. In a preferred embodiment of the present invention, the process produces microflora having a cell aggregate size useful for the production of food products for use in aquaculture. Further disclosed is a food product which includes Thraustochytrium, Schizochytrium, and mixtures thereof, and a component selected from flaxseed, rapeseed, soybean and avocado meal. Such a food product includes a balance of long chain and short chain omega-3 highly unsaturated fatty acids.

Process for the Heterotrophic Production of Microbial Products with High Concentrations of Omega-3 Highly Unsaturated Fatty Acids

About 5,000 strains of marine microorganisms were screened for eicosapentaenoic acid (EPA)-producing ability, which was detected in 88 of them. All of the latter were found to be obligate aerobic, Gram-negative, motile, short rod-shaped bacteria. One strain, designated as SCRC-8132, showed a doubling time of 30 min at 25 degrees C and produced 20 mg/liter (4 mg/g dry cells) when cultured in a P-Y-M-Glucose medium for 18 h. The EPA to total fatty acids ratio was 24%. The strain produced 26 mg EPA/liter (15 mg/g dry cells) when cultured at 4 degrees C for 5 days, the EPA ratio being increased to 40%.

Production of eicosapentaenoic acid by marine bacteria.

A process for the production of (optionally lipid containing) eicosapentaenoic acid comprises the steps of a) culturing a microorganism capable of producing lipid containing eicosapentaenoic acid belonging to the genus Pseudomonas, Alteromonas and Shewanella, to produce lipid containing eicosapentaenoic acid, and b) recovering the (optionally lipid containing) eicosapentaenoic acid from the cultured product. Microorganisms capable of producing eicosapentaenoic acid belonging to the genera Pseudomonas, Alteromonas and Shewanella are also disclosed.

Process for production of eicosapentaenoic acid

The Escherichia coli-Salmonella typhimurium-Salmonella abortus-equi hybrid strain EJ1420 has the two Salmonella flagellin genes fliC (antigenic determinant i) and fljB (determinant e,n,x) at the same loci as in the Salmonella strains and constitutively expresses the fliC gene because of mutations in the genes mediating phase variation. Selection for motility in semisolid medium containing anti-i flagellum serum yielded 11 motile mutants, which had the active fliC(e,n,x) and silent fljB(e,n,x) genes. Genetic analysis and Southern hybridization indicated that they had mutations only in the fliC gene, not in the fljB gene or the control elements for phase variation. Nucleotide sequence analysis of the fliC(e,n,x) genes from four representative mutants showed that the minimum 38% (565 bp) and maximum 68% (1,013 bp) sequences of the fliC(i) gene are replaced with the corresponding sequences of the fljB(e,n,x) gene. One of the conversion endpoints between the two genes lies somewhere in the 204-bp homologous sequence in the 5' constant region, and the other lies in the short homologous sequence of 6, 8, or 38 bp in the 3' constant region. The conversions include the whole central variable region of the fljB gene, resulting in fliC(e,n,x) genes with the same number of nucleotides (1,503 bp) as the fljB gene. We discuss the mechanisms for gene conversion between the two genes and also some intriguing aspects of flagellar antigenic specificities in various Salmonella serovars from the viewpoint of gene conversion.

Conversion of the Salmonella phase 1 flagellin gene fliC to the phase 2 gene fljB on the Escherichia coli K-12 chromosome.

A process for the production of eicosapentaenoic acid comprising the steps of a) culturing a microorganism capable of producing lipid containing eicosapentaenoic acid belonging to a genus selected from the group of Pseudomonas, Alteromonas and Shewanella, to produce lipid containing eicosapentaenoic acid, and b) recovering the eicosapentaenoic acid from the cultured product; a process for production of a lipid containing eicosapentaenoic acid comprising the steps of a) culturing a microorganism capable of producing lipid containing eicosapentaenoic acid belonging to a genus selected from the group of Pseudomonas, Alteromonas and Shewanella, to produce lipid containing eicosapentaenoic acid, and b) recovering the lipid containing eicosapentaenoic acid; and microorganisms capable of producing eicosapentaenoic acid belonging to a genus selected from the group consisting of Pseudomonas, Alteromonas, and Shewanella.

Microbial process for production of eicosapentaenoic acid

We detected inducible melibiose transport activity in cells of Enterobacter cloacae IID977. H+, but not Na+, was found to be the coupling cation for this transporter. We cloned and sequenced the gene encoding the melibiose transporter. A homology search of a protein sequence database revealed that this melibiose transporter has high sequence similarity with the lactose transporter (LacY) and the raffinose transporter (RafB) and has some similarity with the melibiose transporter (MelB) of Escherichia coli.

Noriko Okazaki

Papers

Production of eicosapentaenoic acid by marine bacteria.

Process for production of eicosapentaenoic acid

Conversion of the Salmonella phase 1 flagellin gene fliC to the phase 2 gene fljB on the Escherichia coli K-12 chromosome.

Microbial process for production of eicosapentaenoic acid

A melibiose transporter and an operon containing its gene in Enterobacter cloacae.