Type strains are of huge relevance for Prokaryotic nomenclature because the serve as ☞ nomenclatural types of species and subspecies.
Subtle differences exist between the presentation of type strains in distinct databases. The two major approaches are best illustrated by an example.
Version 1: The type strain of Geodermatophilus sabuli Hezbri et al. 2015 is BMG 8133, which is represented by DSM 46844 and CECT 8820.
Version 2: The type strain of Geodermatophilus sabuli Hezbri et al. 2015 is represented by BMG 8133, DSM 46844 and CECT 8820.
As in many other cases, here BMG 8133 is the original strain name used in the laboratory or institution that conducted the taxon description and whose members (potentially in collaboration with other institutions) proposed the taxon name. DSM 46844 and CECT 8820 are deposits in culture collections, which are needed to ☞ validly publish the taxon name.
Version 1 is hierarchical, as DSM 46844 and CECT 8820 are treated as subordinate to BMG 8133. In version 1, BMG 8133 is a superordinate identifier that could be used in place of the subordinate identifiers DSM 46844 and CECT 8820; it would just be less specific.
In contrast, version 2 is flat. In version 2, all three identifiers have the same rank and are equally specific.
Which representation is preferable? There are a number of reasons to prefer version 2 over version 1 in a database such as LPSN:
The representation of type strains in LPSN thus uses version 2. Analogous arguments could be made for strains that are not type strains.
Databases also differ regarding the usage of the term "proposed type strain" for type strains of names of species or subspecies that are not ☞ validly published.
The ☞ ICNP does neither use nor define the term "proposed type strain". It is actually in conflict with the ICNP to assume that a "proposed type strain" becomes a "type strain" once the name for which this strain serves as the ☞ nomenclatural type becomes validly published. Since having a type strain (as opposed to having a "proposed type strain") is a prerequisite for ☞ names of species and names of subspecies to become validly published [Rule 27(3); Rule 16; Rule 15], the valid publication of a name cannot in turn be a prerequisite for a "proposed type strain" to become a type strain.
Moreover, Rule 18b states: "If the author in the effective publication of the name of a species or subspecies definitely designated a type strain, then this strain shall be accepted as the type strain and may be referred to as the holotype." The rule does not refer to the effective publication having designated a "proposed type strain"; the rule says "type strain". In fact, if the type strain designated in the effective publication was just a "proposed type strain", it would have preliminary status and thus there would not be any need to accept it, contrary to the Rule. It is obvious from Rule 18c that the INCP uses the term "proposed" to indicate the preliminary status of an entity, as a "proposed neotype" can be appealed against. Contrast this with Rule 18b, which determines that a designated type strain has to be accepted and thus cannot be appealed against. Since the ☞ effective publication of a name may precede the valid publication of a name [Rule 27 (2)] it is not in accordance with the ICNP to assume that the valid publication of a name changes a "proposed type strain" to a type strain.
The idea that a "proposed type strain" becomes a type strain via the valid publication of the name of the species or subspecies for which it serves as the nomenclatural type may originate from a misinterpretation of the status of not being validly published. In the ICNP valid publication solely refers to names of taxa but not to names or numbers of strains. If the type strain designated by the authors of the effective publication does not fulfill the ☞ conditions specified by the ICNP, then the name of the species or subspecies for which it serves as the nomenclatural type simply does not become validly published.
LPSN thus does not use the term "proposed type strain" because it is misleading.