Halobacterium salinarum

It is known for rod-shaped, swimming cells and for thriving in extremely salty water, including saturated salt solutions.

The red-orange colour associated with dense cultures comes from pigments called bacterioruberins.

That colour is different from the purple membrane patches containing the light-sensitive protein bacteriorhodopsin.

Its swimming apparatus is an archaellum, built from proteins called archaellins.

These proteins carry attached sugars, and a study that disrupted that modification found defective assembly and impaired movement.

H. salinarum can direct its swimming in response to light, chemicals and oxygen, rather than simply drifting through its environment.

Bacteriorhodopsin is a membrane protein that uses absorbed light to pump protons across the membrane.

The resulting difference across the membrane stores energy that ATP synthase can use to make ATP.

In other words, light is converted into an electrochemical difference before that energy becomes available for cellular work.

The classic 1973 study reported that illuminated purple-membrane-containing cells could maintain a proton gradient under starved or anaerobic conditions.

This light-driven process is therefore not the same as simply using oxygen to release energy from food.

The research-group account also describes energy generation by aerobic metabolism and by arginine fermentation.

Calling the organism unconditionally dependent on oxygen would overlook those distinct energy pathways.

Single-cell observations found that cultured H. salinarum cells elongated between divisions and maintained a relatively narrow size distribution.

The investigators described a tendency to add a consistent amount of length between division events, while individual growth rates and division positions remained variable.

Thus, the population can regulate size without every cell growing or dividing in exactly the same way.

Work using the NRC-1 strain and defined derivatives distinguished the process of elongation from the process of division.

FtsZ2 was required for cell division but not for continued elongation in the studied cells.

The investigators identified regulatory proteins controlling expression of the ftsZ2 gene and proposed that this regulation helps coordinate division timing with growth.

Evaporation can trap small volumes of brine, including microorganisms, inside salt crystals.

In a laboratory study of NRC-1, researchers examined cellular proteins two months after the cells became enclosed in these brine inclusions.

The protein profile resembled that of stationary-phase liquid cultures in several respects, but ribosomal proteins were reduced and movement-associated proteins were absent or less abundant.

This is evidence of acclimation to a particular enclosed, salty microenvironment, not proof that cells remain alive without liquid water.

The same paper explains why the geological age of salt cannot automatically be assigned to the age of living cells recovered from it.

Its two-month laboratory observations do not establish survival for millions of years.

NRC-1 is a named strain within H. salinarum, with its own subordinate NCBI record.

The 2000 genome report described 2,571,010 base pairs distributed across a large chromosome and two smaller replicons.

That is a historical result for NRC-1, not a newly checked genome size for every cell assigned to the species.

The species’ nomenclatural type is represented by designations including DSM 3754 and ATCC 33171, which are not NRC-1.

Keeping the strain name attached to an experimental result helps distinguish observations made in different biological materials.

Is every red or pink salt pond evidence of this one species?

No: the presence of a pigment associated with H. salinarum is not, by itself, an identification of the organisms in an untested sample.

Are Halobacterium halobium and Halobacterium salinarum always different species in older papers?

LPSN lists Halobacterium halobium as a synonym, so historical naming must be checked before treating the names as different organisms.

Does a photograph reveal whether a cell is NRC-1?

No: a strain designation is an identity attached to documented biological material, not a property that can be established from a generic cell silhouette.

The retained article identity is ncbi_taxonomy:2242, currently a species-rank record in Archaea.

NRC-1 is represented separately as ncbi_taxonomy:64091 with a no-rank designation and a co-identical strain designation ATCC 700922.

The nomenclatural type designations listed by LPSN include DSM 3754, ATCC 33171 and NRC 34002; these must not be replaced by NRC-1.

The 1973 photoreceptor paper used the historical name Halobacterium halobium and directly reported light-associated proton movements.

The current naming record supplies a synonym relationship, not evidence that all historical preparations were the NRC-1 strain.

The ATP explanation uses the research group’s stated coupling between the proton gradient and ATP synthase, rather than attributing every later mechanistic conclusion to the early abstract alone.

The 2020 cell-division paper names NRC-1 as its wild-type H. salinarum material and describes defined derivatives.

Its FtsZ2 and regulatory-network findings are retained with that experimental scope rather than treated as a complete division mechanism for all archaea.

Favreau and colleagues’ article was published in January 2023, although its DOI and volume label contain 2022.

The reported proteome comparison concerns a two-month laboratory halite model and does not date cells in ancient natural deposits.

The 2000 NRC-1 genome figure is supported here by an indexed primary abstract, not a newly retrieved accession-version-specific assembly response.

It must therefore remain a dated research result rather than a current annotation count or a species-wide constant.