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Criteria for Accession of New Algal Strains & Taxonomic Considerations for Algal Cultures

Criteria for Accession of New Algal Strains
Taxonomic Considerations for Algal Cultures

Criteria for Accession of New Algal Strains Into the UTEX Collection

In order to balance the desire to maximize the number and diversity of strains to the user community while maintaining the quality of the existing Collection with its limited resources, it is necessary to define criteria for accepting new strains into the UTEX Collection. The criteria listed below are used as a guide to determine which new strains to incorporate, and which lost strains to replace. However, it is impossible to apply these criteria quantitatively since each individual strain has its own unique attributes whose value must be considered.

  1. Practicality of culturing the strain in the existing facilities: Only strains that can be cultured under the conditions accessible to UTEX can be accepted.
  2. Unialgal culture: UTEX only accepts unialgal cultures for inclusion into the permanent Collection. Axenic cultures are preferred and are given priority for acceptance.
  3. Potential value of the strain to research and biotechnology communities: Strains with unique biochemical qualities, those which tolerate extreme conditions, or those which synthesize products of potential economic importance will especially be considered for inclusion in UTEX.
  4. Potential value of the strain to the teaching community: Strains that illustrate diverse morphological, physiological and reproductive strategies of interest to educators will especially be considered for inclusion in UTEX.
  5. Potential value of the strain to various other user communities: Uses include fish or shellfish food, human nutrition supplements, water quality analysis, etc.
  6. Increase in taxonomic breadth of the Collection: Species that increase the genetic diversity, particularly when they are likely to be of value in systematic studies, will especially be considered.
  7. Known strain history and documentation of strain identity: Strains with published descriptions and taxonomic identities will be especially considered for inclusion in UTEX. A strain whose identity is uncertain cannot under most circumstances be accepted until it can be assigned a taxonomic status.
  8. Practicality of providing appropriate culture medium: Strains that can be grown in a medium already prepared routinely for existing UTEX cultures will be favored over strains that require a special medium. Strains requiring medium that is expensive or time-consuming to prepare will be accepted only when other qualities make these strains especially desirable.
  9. Historical value: Strains that have been used extensively in the past as research organisms, and those which have had a significant impact on man's activities will be considered for inclusion in UTEX.
  10. Complementary to another strain in the Collection: Sexually compatible strains that don't self-fertilize will be considered for acceptance into the UTEX Collection even when they appear morphologically identical, in order to provide sexually reproducing species.
  11. Organisms isolated from a natural source: Generally UTEX will accept only strains isolated from natural sources. UTEX cannot accept strains that are proprietary and carry a current patent number for inclusion in the list of available cultures.
Procedure for Accepting a New Algal Strain into UTEX 

An algal strain can only be accepted for inclusion into the permanent UTEX Collection if it:
  • can be made available to the public without proprietary claim;
  • is accompanied by an appropriate description and background information;
  • meets established criteria for accession of new cultures.
The following sequence of events is followed in accessing a new strain for inclusion into the Culture Collection of Algae at The University of Texas.
  1. A unialgal culture of the strain of interest is provided to UTEX for consideration. Any strain submitted for inclusion will be considered, whether or not it was solicited by UTEX. The depositor should use the "Strain Deposition Information" form to submit as much information as possible regarding the strain to be deposited.
  2. Upon its receipt, the strain is assigned a temporary UTEX number for internal use only. It is cultured under conditions that are expected to propagate the strain indefinitely under available conditions.
  3. When the culture has been grown through several transfers to fresh medium without decline in quality or any manifestation of unacceptable contamination, then it is ready for inclusion into the permanent Collection. The depositor is then informed that the strain will be accessed by UTEX, and the strain is assigned a permanent accession number. If the culture cannot be successfully cultured or it is deemed unacceptable for other reasons, then the depositor is informed that the strain cannot be accessed by UTEX, and all cultures of the strain are destroyed.
  4. The accessed strain is moved to its permanent site in the Collection. It is included in the list of cultures on the UTEX web site. Information regarding the strain history, the name of the depositor, suitable culturing conditions, etc. is also listed. The strain is then available to users.

Taxonomic Scope of the Strains in the Culture Collection of Algae

No simple definition can be applied to all organisms that are generally recognized as algae while excluding all organisms that do not appear to be algae. A loose and rather widely recognized definition is as follows: Algae are oxygenic photosynthetic organisms that do not possess a highly differentiated vascular system nor multicellular sterile tissues surrounding their gametes. Stated in slightly expanded form, they are typified by the following characters:
  • Algae generally have the ability to perform photosynthesis with the production of molecular oxygen, which is always associated with the presence of chlorophyll a.
  • Algae generally do not have specialized transport tissues consisting of interconnected cells that move nutrients and metabolites among different sites within the organism.
  • Algae that reproduce sexually produce gametes that generally are not surrounded by specialized protective multicellular parental tissue.
This description distinguishes algae from most plants, animals, fungi, nonphotosynthetic protists and nonoxygenic prokaryotes. It is a practical definition for many ecological and physiological considerations, and is convenient for broad taxonomic identifications. Yet, it has very little phylogenic (evolutionary) relevance. 

The Culture Collection of Algae at the University of Texas at Austin (UTEX) generally adheres to the loose definition given above in determining which strains of living organisms are appropriate to maintain in the Collection. However, a few strains in the Collection fall outside of these boundaries. For example, certain colorless, nonphotosynthetic strains are so similar morphologically and genetically to typical algae that they are universally recognized as belonging to the algae. 

Taxonomic Designations Within the Algae 

The algae fall into two broad categories: cyanobacteria and eukaryotic algae. The cyanobacteria (also called blue-green algae, blue-green bacteria, chloroxybacteria or cyanophytes) are prokaryotic organisms. The eukaryotic algae represent an extremely diverse assemblage of organisms that do not form a coherent phylogenetic group (i.e. they are not monophyletic). 

Traditionally the algae have been classified according to the rules of botanical nomenclature. Accordingly, the primary groupings are designated as "divisions", secondary groupings as "classes", etc. This system is impractical for prokaryotes and has become virtually intractable for protists (including algae) since the organisms associated with these traditional categories do not form well-defined phylogenetic groups. Most traditional divisions of eukaryotic algae are more closely related to major groups of non-algal protists than to any other algal division. Modern methods of phylogenetic analysis, especially DNA sequence data, are continually altering the ways that algae are classified. 

Names and inferred phylogenetic relationships at practically every taxonomic level are in flux for most algal taxa. Thus, it may be impossible to assign names that remain valid over time, or that will be universally accepted even at the time they are assigned. For that reason UTEX does not attempt to determine the most recently assigned names for strains in the Collection. A new strain is accessioned into the Collection only when there is reason to believe that the depositor has correctly identified the strain and designated it with an accurate name based on information available at the time of deposition. The strain is then accessioned under that name. The accession name, along with its corresponding accession number, remains with the strain as long as it is maintained in continuous culture. UTEX personnel do not actively search the literature for revised names, but when UTEX personnel become aware of a name change for a UTEX strain recommended by an established expert, then the new name, along with a reference to the published manuscript describing the change, will be included in the list of cultures. The new name will be listed alphabetically by genus and specific epithet, designated as "a.k.a." and cross-referenced to the accession name. The a.k.a. (aka-nym) designation means that the name is believed correspond to the strain in the Collection listed under a different accessioning name. 

A unique accession number is assigned to each separate isolate accessioned into the Collection. Thus, no two isolates in UTEX are ever assigned the same number, and no isolate is assigned more than one number. Even when an accessioned strain has been lost for many years, its accession number is not re-assigned to a different isolate. 

Replacement of UTEX Strains That Have Been Lost to the Collection 

On occasion a strain that previously had been accessioned is lost. Under most circumstances the accession number is then retired, and is never used again for a UTEX strain. Any other accessioned isolate, even it is appears identical to the lost strain and is isolated from the same location as was the lost strain, is assigned a different accession number. 

When the same isolate prepared as a unialgal culture is deposited in UTEX and also in another collection, then a replacement culture may be requested from the other collection if the strain is lost to UTEX. Under this circumstance the acquired culture will be assigned the same accession number as the culture originally deposited in UTEX. The primary name of the strain will be assigned the name under which it is listed in the other collection, which may not be the same as the name of under which the strain was first accessioned by UTEX. 

Verification of the Taxonomic Identity of UTEX Strains 

Only unialgal strains are accessioned into the collection, and only when identified and named by an established authority. UTEX makes no guarantee regarding the correct and most recent names of strains held in the Collection. Nor do UTEX personnel systematically examine strains in the Collection to assure their correct taxonomic identity. 

In order to maintain healthy cultures many hundreds of algal transfers are made every month. Although internal checks eliminate nearly all mistakes, on rare occasion a culture is mislabeled or is contaminated with another strain. Any culture that appears to be mislabeled is immediately discarded. Cultures of uncertain strain identity are discarded even if that means the permanent loss of an accessioned UTEX strain.