Major Streptomyces species associated with fissure scab of potato in South Africa including description of Streptomyces solaniscabiei sp. nov.

Streptomyces species are the causal agents of several scab diseases on potato tubers. A new type of scab symptom, caused by Streptomyces species, was observed in South Africa from 2010 onwards. The disease was initially thought to be caused by a single Streptomyces species, however, subsequent isolations from similar symptoms on other potato tubers revealed diversity of the Streptomyces isolates. The objective of this study was to characterise these isolates in order to determine what are the major species involved in the disease. This was done by sequencing and phylogenetic analyses of the 16S rDNA as well as five housekeeping genes, investigation of growth on different culture media, standard phenotypic tests and scanning electron microscopy of culture morphology. The presence of the pathogenicity island (PAI) present in plant pathogenic Streptomyces species was also investigated. The genomes of eight isolates, selected from the three main clades identified, were sequenced and annotated to further clarify species boundaries. Three isolates of each of the three main clades were also inoculated onto susceptible potato cultivars in order to establish the pathogenicity of the species. The results of the phylogenetic and genome analyses revealed that there are three main species involved, namely, Streptomyces werraensis, Streptomyces pseudogriseolus and a novel Streptomyces species that is described here as Streptomyces solaniscabiei sp. nov., with strain FS70T (= PPPPB BD 2226T = LMG 32103T) as the type strain. The glasshouse trial results showed that all three of the Streptomyces species are capable of producing fissure scab symptoms. None of the Streptomyces isolates from fissure scab contained the full PAI and the mechanism of disease initiation still needs to be determined. Genomic comparisons also indicated that S. gancidicus Suzuki 1957 (Approved Lists 1980) is a later heterotypic synonym of S. pseudogriseolus Okami and Umezawa 1955 (Approved Lists 1980).

Taxonomic evaluation of Streptomyces albus and related species using multilocus sequence analysis and proposals to emend the description of Streptomyces albus and describe Streptomyces pathocidini sp. nov.

In phylogenetic analyses of the genus Streptomyces using 16S rRNA gene sequences, Streptomyces albus subsp. albus NRRL B-1811(T) forms a cluster with five other species having identical or nearly identical 16S rRNA gene sequences. Moreover, the morphological and physiological characteristics of these other species, including Streptomyces almquistii NRRL B-1685(T), Streptomyces flocculus NRRL B-2465(T), Streptomyces gibsonii NRRL B-1335(T) and Streptomyces rangoonensis NRRL B-12378(T) are quite similar. This cluster is of particular taxonomic interest because Streptomyces albus is the type species of the genus Streptomyces. The related strains were subjected to multilocus sequence analysis (MLSA) utilizing partial sequences of the housekeeping genes atpD, gyrB, recA, rpoB and trpB and confirmation of previously reported phenotypic characteristics. The five strains formed a coherent cluster supported by a 100 % bootstrap value in phylogenetic trees generated from sequence alignments prepared by concatenating the sequences of the housekeeping genes, and identical tree topology was observed using various different tree-making algorithms. Moreover, all but one strain, S. flocculus NRRL B-2465(T), exhibited identical sequences for all of the five housekeeping gene loci sequenced, but NRRL B-2465(T) still exhibited an MLSA evolutionary distance of 0.005 from the other strains, a value that is lower than the 0.007 MLSA evolutionary distance threshold proposed for species-level relatedness. These data support a proposal to reclassify S. almquistii, S. flocculus, S. gibsonii and S. rangoonensis as later heterotypic synonyms of S. albus with NRRL B-1811(T) as the type strain. The MLSA sequence database also demonstrated utility for quickly and conclusively confirming that numerous strains within the ARS Culture Collection had been previously misidentified as subspecies of S. albus and that Streptomyces albus subsp. pathocidicus should be redescribed as a novel species, Streptomyces pathocidini sp. nov., with the type strain NRRL B-24287(T).

Phylogenetic study of the species within the family Streptomycetaceae.

Species of the genus Streptomyces, which constitute the vast majority of taxa within the family Streptomycetaceae, are a predominant component of the microbial population in soils throughout the world and have been the subject of extensive isolation and screening efforts over the years because they are a major source of commercially and medically important secondary metabolites. Taxonomic characterization of Streptomyces strains has been a challenge due to the large number of described species, greater than any other microbial genus, resulting from academic and industrial activities. The methods used for characterization have evolved through several phases over the years from those based largely on morphological observations, to subsequent classifications based on numerical taxonomic analyses of standardized sets of phenotypic characters and, most recently, to the use of molecular phylogenetic analyses of gene sequences. The present phylogenetic study examines almost all described species (615 taxa) within the family Streptomycetaceae based on 16S rRNA gene sequences and illustrates the species diversity within this family, which is observed to contain 130 statistically supported clades, as well as many unsupported and single member clusters. Many of the observed clades are consistent with earlier morphological and numerical taxonomic studies, but it is apparent that insufficient variation is present in the 16S rRNA gene sequence within the species of this family to permit bootstrap-supported resolution of relationships between many of the individual clusters.

Reassessment of the systematics of the suborder Pseudonocardineae: transfer of the genera within the family Actinosynnemataceae Labeda and Kroppenstedt 2000 emend. Zhi et al. 2009 into an emended family Pseudonocardiaceae Embley et al. 1989 emend. Zhi et al. 2009.

The taxonomic status of the families Actinosynnemataceae and Pseudonocardiaceae was assessed based on 16S rRNA gene sequence data available for the 151 taxa with validly published names, as well as chemotaxonomic and morphological properties available from the literature. 16S rRNA gene sequences for the type strains of all taxa within the suborder Pseudonocardineae were subjected to phylogenetic analyses using different algorithms in arb and phylip. The description of many new genera and species within the suborder Pseudonocardineae since the family Actinosynnemataceae was proposed in 2000 has resulted in a markedly different distribution of chemotaxonomic markers within the suborder from that observed at that time. For instance, it is noted that species of the genera Actinokineospora and Allokutzneria contain arabinose in whole-cell hydrolysates, which is not observed in the other genera within the Actinosynnemataceae, and that there are many genera within the family Pseudonocardiaceae as currently described that do not contain arabinose. Phylogenetic analyses of 16S rRNA gene sequences for all taxa within the suborder do not provide any statistical support for the family Actinosynnemataceae, nor are signature nucleotides found that support its continued differentiation from the family Pseudonocardiaceae. The description of the family Pseudonocardiaceae is therefore emended to include the genera previously classified within the family Actinosynnemataceae and the description of the suborder Pseudonocardineae is also emended to reflect this reclassification.

Emended description of the genus Actinokineospora Hasegawa 1988 and transfer of Amycolatopsis fastidiosa Henssen et al. 1987 as Actinokineospora fastidiosa comb. nov.

The species Amycolatopsis fastidiosa (ex Celmer et al. 1977) Henssen et al. 1987 was proposed, based on morphological and chemotaxonomic observations, for a strain originally described as 'Pseudonocardia fastidiosa' Celmer et al. 1977 in a US patent. In the course of a phylogenetic study of the taxa with validly published names within the suborder Pseudonocardineae based on 16S rRNA gene sequences, it became apparent that this species was misplaced in the genus Amycolatopsis. After careful evaluation of the phylogeny, morphology, chemotaxonomy and physiology of the type strain, it was concluded that this strain represents a species of the genus Actinokineospora that is unable to produce motile spores. The description of the genus Actinokineospora is therefore emended to accommodate species that do not produce motile spores, and it is proposed that Amycolatopsis fastidiosa be transferred to the genus Actinokineospora as Actinokineospora fastidiosa comb. nov. The type strain is NRRL B-16697(T) =ATCC 31181(T) =DSM 43855(T) =JCM 3276(T) =NBRC 14105(T) =VKM Ac-1419(T).

Streptomyces atriruber sp. nov. and Streptomyces silaceus sp. nov., two novel species of equine origin.

Two actinomycete strains, NRRL B-24165(T) and NRRL B-24166(T), isolated from lesions on equine placentas in Kentucky, USA, were analysed using a polyphasic taxonomic approach. On the basis of phylogenetic analysis of 16S rRNA gene sequences, morphological observations and the presence of ll-diaminopimelic acid as the diagnostic diamino acid in whole-cell hydrolysates, the new isolates clearly belonged to the genus Streptomyces. Analyses of the phylogenetic positions of strains NRRL B-24165(T) and NRRL B-24166(T) based on 16S rRNA gene sequences of all recognized species of the genus Streptomyces, as well as evaluation of morphological and physiological characteristics, demonstrated that the new isolates could be differentiated from all recognized species and therefore represented novel species. It is proposed that the new strains represent two novel species for which the names Streptomyces atriruber sp. nov. (type strain NRRL B-24165(T)=DSM 41860(T)=LDDC 6330-99(T)) and Streptomyces silaceus sp. nov. (NRRL B-24166(T)=DSM 41861(T)=LDDC 6638-99(T)) are proposed. The species names are based on the distinctive colours of the substrate mycelium of these strains, dark red and deep orange-yellow, respectively.

Proposal for the new genus Allokutzneria gen. nov. within the suborder Pseudonocardineae and transfer of Kibdelosporangium albatum Tomita et al. 1993 as Allokutzneria albata comb. nov.

During the course of phylogenetic analyses based on 16S rRNA gene sequences for all currently described taxa within the family Pseudonocardineae, it became evident that Kibdelosporangium albatum DSM 44149(T) was misplaced within the genus Kibdelosporangium and is phylogenetically most closely related to the genus Kutzneria. Chemotaxonomic analyses revealed that Kibdelosporangium albatum differed from Kutzneria in containing arabinose as well as galactose and mannose as diagnostic whole-cell sugars. The polar lipid pattern was distinct from both Kibdelosporangium and Kutzneria species in containing phosphatidylethanolamine containing 2-hydroxy fatty acids, lyso-phosphatidylethanolamine and lyso-phosphatidylmethylethanolamine as well as phosphatidylethanolamine, phosphatidylmethylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. These data preclude the inclusion of this strain within the genus Kutzneria or Kibdelosporangium and a new genus is proposed, to be named Allokutzneria gen. nov. The type species of this new genus is Allokutzneria albata gen. nov., comb. nov., the type strain of which is R761-7(T) (=NRRL B-24461(T) =DSM 44149(T) =ATCC 55061(T)).

Proposal of Goodfellowiella gen. nov. to replace the illegitimate genus name Goodfellowia Labeda and Kroppenstedt 2006.

The prokaryotic, generic name Goodfellowia Labeda and Kroppenstedt 2006 is illegitimate because it is a later homonym of the name Goodfellowia Hartert, 1903 (Animalia, Chordata, Aves, Passeriformes, Sturnidae) [Principle 2 of the Bacteriological Code (1990 Revision)]. A new genus name, Goodfellowiella, is therefore proposed for this taxon (Rule 54). This also requires that a new combination, Goodfellowiella coeruleoviolacea comb. nov., be proposed for the type species to replace the illegitimate combination Goodfellowia coeruleoviolacea (Preobrazhenskaya and Terekhova 1987) Labeda and Kroppenstedt 2006.

Proposal of Umezawaea gen. nov., a new genus of the Actinosynnemataceae related to Saccharothrix, and transfer of Saccharothrix tangerinus Kinoshita et al. 2000 as Umezawaea tangerina gen. nov., comb. nov.

In the course of phylogenetic analyses of the taxa within the suborder Pseudonocardineae, it was observed that Saccharothrix tangerinus MK27-91F2(T) was misplaced in the genus Saccharothrix. After a detailed examination of nucleotide signatures in the 16S rRNA gene sequence along with the morphological and chemotaxonomic characteristics of this strain, which are different from those of all species of Saccharothrix as well as the other genera within the suborder, it was concluded that this strain represents a new genus, for which the name Umezawaea gen. nov. is proposed. Pseudosporangia are produced on the aerial mycelium, the whole-cell sugar pattern consists of galactose, mannose and ribose, phosphatidylethanolamine, phosphatidylinositol and lyso-phosphatidylethanolamine are the predominant phospholipids and MK-9(H(4)) is the predominant menaquinone. The type species of the proposed new genus is Umezawaea tangerina gen. nov., comb. nov., with the type strain MK27-91F2(T) (=NRRL B-24463(T) =DSM 44720(T) =FERM P-16053(T) =JCM 10302(T) =NBRC 16184(T)).

Recommendation for the conservation of the name Streptomyces scabies. Request for an Opinion.

The primary streptomycete inciting common scab of potato was first legitimately described by Thaxter in 1892 as 'Oospora scabies', preserving the spelling of an epithet in use since 1846. The name Streptomyces scabies, dating to 1948, was revived in 1989, but changed to Streptomyces scabiei in 1997 to follow grammatical convention. Considering the long-established use and general recognition of 'scabies', it is proposed that the original epithet be conserved.

Lentzea kentuckyensis sp. nov., of equine origin.

A novel actinomycete, designated strain LDDC 2876-05(T), was isolated from an equine placenta during the course of routine diagnostic tests for nocardioform placentitis. In a preliminary study, the strain was observed to be phylogenetically distinct from the genera Crossiella and Amycolatopsis and probably a member of the genus Lentzea. A polyphasic study of strain LDDC 2876-05(T) confirmed its identification as a member of Lentzea on the basis of its chemotaxonomic and morphological similarity to all of the known species of the genus. Moreover, the strain could be distinguished from other species with validly published names on the basis of its phylogenetic and physiological characteristics and its fatty acid profile. Therefore strain LDDC 2876-05(T) represents a novel species of the genus Lentzea, for which the name Lentzea kentuckyensis sp. nov. is proposed. The type strain is LDDC 2876-05(T) (=NRRL B-24416(T) =DSM 44909(T)).

Goodfellowia gen. nov., a new genus of the Pseudonocardineae related to Actinoalloteichus, containing Goodfellowia coeruleoviolacea gen. nov., comb. nov.

During the course of a phylogenetic evaluation of Saccharothrix strains held in the ARS Culture Collection, it was discovered that Saccharothrix coeruleoviolacea NRRL B-24058(T) is unrelated to other species within this genus, and a polyphasic study was undertaken to clarify its taxonomic position. Strain NRRL B-24058(T) is observed to be phylogenetically separate from the genus Saccharothrix and is most closely related to the genus Actinoalloteichus. The strain exhibits chemotaxonomic properties that distinguish it from members of Actinoalloteichus, including a whole-cell sugar pattern consisting of galactose and ribose as diagnostic sugars, phosphatidylethanolamine, phosphatidylethanolamine containing 2-OH fatty acids and diphosphatidylglycerol as the predominant polar lipids and MK-9(H(4)) and MK-10(H(4)) as the only menaquinones observed. Strain NRRL B-24058(T) is distinct from other taxa within the suborder Pseudonocardineae and a new genus to be named Goodfellowia gen. nov. is proposed. The type species of this new genus is Goodfellowia coeruleoviolacea gen. nov., comb. nov., and the type strain is NRRL B-24058(T) (=DSM 43935(T) = INA 3564(T) = JCM 9110(T) = NBRC 14988(T) = VKM Ac-1083(T)).

Stackebrandtia nassauensis gen. nov., sp. nov. and emended description of the family Glycomycetaceae.

During the course of a 16S rRNA gene sequence phylogenetic evaluation of putative Glycomyces strains, it was noted that strain NRRL B-16338(T) is phylogenetically nearest to the genus Glycomyces but apparently is not a member of this or any of the other currently described actinomycete genera. The strain was subjected to a polyphasic study using standard methods for chemotaxonomic, morphological and physiological evaluation. The strain exhibited chemotaxonomic characteristics distinct from Glycomyces in spite of having 16S rRNA gene sequence similarity of 92% with the described species of this genus. The whole-cell sugar pattern of NRRL B-16338(T) consisted of ribose and inositol, with traces of arabinose and mannose. The phospholipids observed were phosphatidylglycerol and diphosphatidylglycerol and menaquinones consisting of MK-10(H(4)), MK-10(H(6)), MK-11(H(4)) and MK-11(H(6)). A significant quantity (14.5%) of 17:0 anteiso 2-hydroxy fatty acid was observed in the fatty acid profile of this strain. These characteristics clearly differentiate NRRL B-16338(T) from members of the genus Glycomyces and it is proposed that the strain represents a new genus within the family Glycomycetaceae to be called Stackebrandtia gen. nov. The description of this family is emended to permit its inclusion. It is proposed that the type species of the genus should be named Stackebrandtia nassauensis. The type strain LLR-40K-21(T) (=NRRL B-16338(T)=DSM 44728(T)) was isolated from a soil sample from Nassau, Bahamas.

Saccharothrix algeriensis sp. nov., isolated from Saharan soil.

The taxonomic position of a soil isolate, strain SA 233T, recovered from Saharan soil from Algeria was established using a polyphasic approach. This isolate has been previously reported to produce three novel dithiolopyrrolone antibiotics, and preliminary chemotaxonomic and morphological characteristics suggested that it was representative of a member of the genus Saccharothrix. Phylogenetic analysis of the strain from 16S rDNA sequences, along with a detailed analysis of morphological, chemotaxonomic and physiological characteristics, indicates that it belongs to the genus Saccharothrix and represents a novel species that is readily distinguished from all recognized Saccharothrix species. The name Saccharothrix algeriensis sp. nov. is proposed for the isolate, with type strain SA 233T (=NRRL B-24137T=DSM 44581T).

Amycolatopsis kentuckyensis sp. nov., Amycolatopsis lexingtonensis sp. nov. and Amycolatopsis pretoriensis sp. nov., isolated from equine placentas.

Actinomycete strains isolated from lesions on equine placentas from two horses in Kentucky and one in South Africa were subjected to a polyphasic taxonomic study. Chemotaxonomic and morphological characteristics indicated that the isolates are members of the genus AMYCOLATOPSIS: On the basis of phylogenetic analysis of 16S rDNA sequences, the isolates are related most closely to Amycolatopsis mediterranei. Physiological characteristics of these strains indicated that they do not belong to A. mediterranei and DNA relatedness determinations confirmed that these strains represent three novel species of the genus Amycolatopsis, for which the names Amycolatopsis kentuckyensis (type strain, NRRL B-24129(T)=LDDC 9447-99(T)=DSM 44652(T)), Amycolatopsis lexingtonensis (type strain, NRRL B-24131(T)=LDDC 12275-99(T)=DSM 44653(T)) and Amycolatopsis pretoriensis (type strain, NRRL B-24133(T)=ARC OV1 0181(T)=DSM 44654(T)) are proposed.

Crossiella equi sp. nov., isolated from equine placentas.

Over the course of the past decade, actinomycetes have been isolated from the placentas of horses diagnosed with nocardioform placentitis. The incidence of this infection has generally been low, with typically no more than 30 animals affected in most years, but the incidence increased through 1999, with placentas from 144 mares found to be infected. Approximately half of the cases result in loss of the foal. A typical actinomycete with branching mycelium was isolated from placental lesions, and a comparison of the sequence of the 16S rDNA gene against the public databases indicated a relationship to members of the suborder Pseudonocardineae. Phylogenetic analysis of representative isolates revealed a close relationship to Crossiella cryophila, and subsequent polyphasic comparisons determined that these isolates represent a novel species of Crossiella, for which the name Crossiella equi sp. nov. is proposed, with strain LDDC 22291-98(T) (= NRRL B-24104(T) = DSM 44580(T)) as the type strain.

Crossiella gen. nov., a new genus related to Streptoalloteichus.

Phylogenetic analysis of the genera within the suborder Pseudonocardineae based on almost complete sequences of 16S rDNA showed that Saccharothrix cryophilis NRRL B-16238T was misplaced within the genus Saccharothrix. Saccharothrix cryophilis NRRL B-16238T appeared to be phylogenetically closest to Streptoalloteichus, but is morphologically distinct from this genus because sporangia with motile spores are not observed. The aerial mycelium fragments into rod-shaped elements and sclerotium-like bodies are observed occasionally in the substrate mycelium. The cell wall contains meso-diaminopimelic acid, whole-cell hydrolysates contain galactose, rhamnose and ribose, the phospholipid pattern is type PIV and the principal menaquinone is MK-9(H4). A new genus to accommodate Saccharothrix cryophilis is proposed, Crossiella gen. nov., in recognition of the contributions of Thomas Cross, a distinguished actinomycete biologist at the University of Bradford, UK. The type species is Crossiella cryophila gen. nov., comb. nov.

Revival of the genus Lentzea and proposal for Lechevalieria gen. nov.

The genus Saccharothrix is phylogenetically heterogeneous on the basis of analysis of almost complete 16S rDNA sequences. An evaluation of chemotaxonomic, morphological and physiological properties in the light of the molecular phylogeny data revealed that several species are misclassified. Saccharothrix aerocolonigenes NRRL B-3298T and Saccharothrix flava NRRL B-16131T constitute a lineage distinct from Saccharothrix and separate from Lentzea. The genus Lechevalieria gen. nov. is proposed for these species. Lechevalieria aerocolonigenes comb. nov. is the type species and S. flava is transferred as Lechevalieria flava comb. nov. Although Lentzea albidocapillata, the type species of the genus Lentzea, was transferred recently to the genus Saccharothrix, the revival of Lentzea is clearly supported by molecular phylogenetic and chemotaxonomic data. The description of the revived genus is emended to include galactose, mannose and traces of ribose as diagnostic whole-cell sugars and MK-9(H4) as the principal menaquinone and elimination of tuberculostearic acid as a diagnostic component in the fatty acid profile. Saccharothrix waywayandensis NRRL B-16159T, S. aerocolonigenes NRRL B-16137 and 'Asiosporangium albidum' IFO 16102 are members of the amended genus Lentzea on the basis of phylogenetic and chemotaxonomic properties. S. waywayandensis is transferred to Lentzea as Lentzea waywayandensis comb. nov., while the new species Lentzea californiensis sp. nov. and Lentzea albida sp. nov. are described for S. aerocolonigenes NRRL B-16137 and 'A. albidum' IFO 16102, respectively. Nucleotide signatures in the 16S rDNA sequences are defined that are diagnostic for the genera Lechevalieria, Lentzea and Saccharothrix.

Phylogenetic analysis of Saccharothrix and related taxa: proposal for Actinosynnemataceae fam. nov.

Partial sequences for 16S rDNA were determined for strains of the genus Saccharothrix, including most described species, as well as strains of the described species of the related genera Kutzneria, Actinokineospora and Actinosynnema. These were aligned with published sequences for other species of these genera, as well as those of the genera 'Actinoalloteichus', 'Asiosporangium', Lentzea, Kutzneria, Streptoalloteichus and representative taxa from other actinomycete families. Phylogenetic analysis of the sequence data showed that species of the genera Actinokineospora, Actinosynnema, Lentzea and Saccharothrix are members of the same clade, and distinct from the Pseudonocardiaceae. It is proposed that a new family be created within the class Actinobacteria for these genera, to be called the Actinosynnemataceae on the basis of the oldest described genus within this family, Actinosynnema Hasegawa et al. The chemotaxonomic properties of all the genera to be placed within the new family have similar cell wall type (type III), whole-cell sugars (generally galactose although mannose and rhamnose may be present), phospholipid type (PII) and menaquinones [MK-9(H4) predominant].

Critical role of anteiso-C15:0 fatty acid in the growth of Listeria monocytogenes at low temperatures.

Listeria monocytogenes is a food-borne pathogen capable of growth at refrigeration temperatures. Membrane lipid fatty acids are major determinants of a sufficiently fluid membrane state to allow growth at low temperatures. L. monocytogenes was characterized by a fatty acid profile dominated to an unusual extent (> 95%) by branched-chain fatty acids, with the major fatty acids being anteiso-C15:0, anteiso-C17:0, and iso-C15:0 in cultures grown in complex or defined media at 37 degrees C. Determination of the fatty acid composition of L. monocytogenes 10403S and SLCC 53 grown over the temperature range 45 to 5 degrees C revealed two modes of adaptation of fatty acid composition to lower growth temperatures: (i) shortening of fatty acid chain length and (ii) alteration of branching from iso to anteiso. Two transposon Tn917-induced cold-sensitive mutants incapable of growth at low temperatures had dramatically altered fatty acid compositions with low levels of i-C15:0, a-C15:0, and a-C17:0 and high levels of i-C14:0, C14:0, i-C16:0, and C16:0. The levels of a-C15:0 and a-C17:0 and the ability to grow at low temperatures were restored by supplementing media with 2-methylbutyric acid, presumably because it acted as a precursor of methylbutyryl coenzyme A, the primer for synthesis of anteiso odd-numbered fatty acids. When mid-exponential-phase 10403S cells grown at 37 degrees C were temperature down-shocked to 5 degrees C they were able, for the most part, to reinitiate growth before the membrane fatty acid composition had reset to a composition more typical for low-temperature growth. No obvious evidence was found for a role for fatty acid unsaturation in adaptation of L. monocytogenes to cold temperature. The switch to a fatty acid profile dominated by a-C15:0 at low temperatures and the association of cold sensitivity with deficiency of a-C15:0 focus attention on the critical role of this fatty acid in growth of L. monocytogenes in the cold, presumably through its physical properties and their effects, in maintaining a fluid, liquid-crystalline state of the membrane lipids.