DNA base composition of species of the genusSaccharomyces

DNA base compositions (GC content) ofSaccharomyces species are reported and discussed. Several amendments of the four groups given by van der Walt are suggested, viz. the transfer ofS. kluyveri to group 1, and ofS. eupagycus, S. cidri, S. montanus, S. microellipsodes andS. florentinus to group 2. The synonomy ofS. amurcae andS. cidri is suggested. The DNA base compositions revealed two possible pairs of sibling species:S. elegans andS. bailii, with a difference in GC content of 4.1%;S. dairensis andS. servazzii with a difference in GC content of ca. 3%.S. mrakii had a GC content of 47.3–48.5% the highest encountered in this genus and similar to that ofKluyveromyces thermotolerans.     

Floral traits, pollinators and breeding systems in Syncolostemon (Lamiaceae)

Differentiation in floral traits among clusters of related species may reflect a process of pollinator-driven evolution. Pollination systems in the morphologically diverse southern African genus Syncolostemon (Lamiaceae) were investigated by means of field observations of floral visitors and analysis of their pollen loads. Among the five study species, those with short corolla tubes (S. parviflorus, S. ramulosus) were pollinated solely by bees, while those with long corolla tubes were pollinated by a broader array of visitors, primarily long-proboscid flies in S. rotundifolius and S. macranthus and sunbirds in S. densiflorus. The predominately insect-pollinated taxa have lax inflorescences, but S. densiflorus has a compact terminal inflorescence, which facilitates feeding by sunbirds from a single perching position. Experimental hand-pollinations involving three taxa (S. macranthus, S. densiflorus, and S. rotundifolius) showed that these possess a genetic self-incompatibility system. Production of fruits and seeds per fruit was pollen-limited in S. densiflorus and S. rotundifolius, but not in S. macranthus.     

Flavonoid variation in some North Americna Saxifraga species

Eight species of Saxifraga representing sections Micranthes, Hirculus, Dactyloides and Xanthizoon were studied for their flavonoids (S. california, S. integrifolia, S. michauxii, S. ferruginea, S. eschscholtzii, S. hirculus, S. caespitosa and S. aizoides). The major compounds present in most species were kaempferol and quercetin monogluocosides and galactosides. Glucosides of kaempferol and quercetin predominate in the first four species listed, while galactosides of quercetin and myricetin are dominant in the lastthree. 3-O-Methyl- and 3,3′-di-O-methylquercetin were identified from S. californica and S. integrifolia. Saxifraga caespitosa synthesizes a complex mixture of O-methylated flavonols as well as a novel O-methylated dihydrokaempferol.Species pairs S. michauxii/S. ferruginea and S. californica/S.integrifolia exhibit close flavonoid similarity which may reflect their morphological similarities.     

A review of the genus Strigivenifera Hering, 1937 (Lepidoptera, Chrysopolomidae) with a description of ten new species

Twelve species are considered within the Afrotropical genus Strigivenifera Hering, 1937, and ten of them are described as new ones: S. eborea sp. n.,S. livingstonei sp. n., S. marina sp. n., S. tanja sp. n., S. ocellaris sp. n., S. cruisa sp. n., S. bartschi sp. n., S. oris sp. n., S. tatooifera sp. n., and S. neo sp. n. The species S. albidiscalis (Hampson, 1910) is raised from synonymy with S. venata (Aurivillius, 1895) and considered as a separate species.     

CONTROL OF 5S RNA SYNTHESIS DURING EARLY DEVELOPMENT OF ANUCLEOLATE AND PARTIAL NUCLEOLATE MUTANTS OF XENOPUS LAEVIS

Ribosomes of all eukaryotes contain a single molecule of 5S, 18S, and 28S RNA. In the frog Xenopus laevis the genes which code for 18S and 28S RNA are located in the nucleolar organizer, but these genes are not linked to the 5S RNA genes. Therefore the synthesis of the three ribosomal RNAs provides a model system for studying interchromosomal aspects of gene regulation. In order to determine if the synthesis of the three ribosomal RNAs are interdependent, the relative rate of 5S RNA synthesis was measured in anucleolate mutants (o/o), which do not synthesize any 18S or 28S RNA, and in partial nucleolate mutants (p^l-1/o), which synthesize 18S and 28S RNA at 25% of the normal rate. Since the o/o and p^l-1/o mutants have a complete and partial deletion of 18S and 28S RNA genes respectively, but the normal number of 5S RNA genes, they provide a unique system in which to study the dependence of 5S RNA synthesis on the synthesis of 18S and 28S RNA. Total RNA was extracted from embryos labeled during different stages of development and analyzed by polyacrylamide gel electrophoresis. Quite unexpectedly it was found that 5S RNA synthesis in o/o and p^l-1/o mutants proceeds at the same rate as it does in normal embryos. Furthermore, 5S RNA synthesis is initiated normally at gastrulation in o/o mutants in the complete absence of 18S and 28S RNA synthesis.     

Chromosomal mapping,differential origin and evolution of the S100 gene family

S100 proteins are calcium-binding proteins, which exist only in vertebrates and which constitute a large protein family. The origin and evolution of the S100 family in vertebrate lineages remain a challenge. Here, we examined the synteny conservation of mammalian S100A genes by analysing the sequence of available vertebrate S100 genes in databases. Five S100A gene members, unknown previously, were identified by chromosome mapping analysis. Mammalian S100A genes are duplicated and clustered on a single chromosome while two S100A gene clusters are found on separate chromosomes in teleost fish, suggesting that S100A genes existed in fish before the fish-specific genome duplication took place. During speciation, tandem gene duplication events within the cluster of S100A genes of a given chromosome have probably led to the multiple members of the S100A gene family. These duplicated genes have been retained in the genome either by neofunctionalisation and/or subfunctionalisation or have evolved into non-coding sequences. However in vertebrate genomes, other S100 genes are also present i.e. S100P, S100B, S100G and S100Z, which exist as single copy genes distributed on different chromosomes, suggesting that they could have evolved from an ancestor different to that of the S100A genes.     

Population genetics study of Strongyloides fuelleborni and phylogenetic considerations on primate-infecting species of Strongyloides based on their mitochondrial genome sequences

Strongyloides is a genus of parasitic nematodes of vertebrates comprising approximately 50 documented species, each with various host ranges. Among these, three species (S. stercoralis, S. fuelleborni, and S. cebus) are known to infect primate hosts. S. fuelleborni typically infects non-human primates in the Old World. To complement the existing information on the global genetic structure of this species, we conducted a genotyping study of S. fuelleborni samples collected from rhesus macaques in Myanmar, Japanese macaques in Japan, and some zoo-kept primates. This study identified a novel haplotype group in isolates from the Myanmar rhesus macaques. Subsequently, we obtained the complete or nearly complete mitochondrial genome sequences of S. fuelleborni, S. cebus (Strongyloides of New World monkeys), and S. vituli (Strongyloides of cattle). Phylogenetic analysis based on concatenated mitochondrial protein sequences of various Strongyloides species indicated a close relationship between S. fuelleborni, S. vituli and S. papillosus (Strongyloides in sheep and cattle). S. cebus is quite distantly related to both S. fuelleborni and S. stercoralis, which led to the hypothesis that the three primate Strongyloides species evolved independently as parasites of primates.     

Proposal to reclassify the Streptomyces albidoflavus clade on the basis of multilocus sequence analysis and DNA–DNA hybridization,and taxonomic elucidation of Streptomyces griseus subsp. solvifaciens

The Streptomyces albidoflavus 16S rRNA gene clade contains 10 species and subspecies with identical 16S rRNA gene sequences and very similar numerical taxonomic data, including Streptomyces griseus subsp. solvifaciens. Type strains of this clade, as well as three CGMCC strains which were received as Streptomyces galilaeus, Streptomyces sioyaensis and Streptomyces vinaceus, respectively, that shared the same 16S rRNA gene sequences with the clade, were subjected to multilocus sequence analysis (MLSA), DNA–DNA hybridization (DDH) and phenotypic characterization for a comprehensive reevaluation. The 13 strains still formed a distinct, albeit loosely related, clade in the phylogenetic tree based on concatenated sequences of aptD, gyrB, recA, rpoB and trpB genes, supported by a high bootstrap value and different tree-making algorithms, with MLSA evolutionary distances ranging from 0 to 0.003. DDH values among these strains were well above the 70% cut-off point for species delineation. Based on the genotypic data of MLSA and DDH, combined with key phenotypic properties in common, it is proposed that the 10 species and subspecies of the S. albidoflavus clade, namely S. albidoflavus, S. canescens, S. champavatii, S. coelicolor, S. felleus, S. globisporus subsp. caucasicus, S. griseus subsp. solvifaciens, S. limosus, S. odorifer and S. sampsonii, should be merged into a single genomic species, for which the name S. albidoflavus is retained, and that the three strains S. galilaeus CGMCC 4.1320, S. sioyaensis CGMCC 4.1306 and S. vinaceus CGMCC 4.1305 should be assigned to S. albidoflavus as well. The results also indicated that MLSA could be the procedure of choice for distinguishing between species within Streptomyces 16S rRNA gene clades.     

Genetic analysis reveals candidate species in the Scinax catharinae clade (Amphibia: Anura) from Central Brazil

Scinax (Anura: Hylidae) is a species-rich genus of amphibians (113 spp.), divided into five species groups by morphological features. Cladistic analyses however revealed only two monophyletic clades in these groups: Scinax catharinae and Scinax ruber. Most species from the S. catharinae clade are found in Atlantic rainforest, except for Scinax canastrensis,S. centralis, S. luizotavioi, S. machadoi,S. pombali and S. skaios. In the present work, specimens of Scinax collected in Chapada dos Guimarães, central Brazil, were morphologically compatible with species from theS. catharinae group. On the other hand, genetic analysis based on mitochondrial (16S and 12S) and nuclear (rhodopsin) sequences revealed a nucleotide divergence of 6 to 20% between Scinax sp. and other congeners from the Brazilian savannah (Cerrado). Accordingly, Bayesian inference placed Scinax sp. in the S. catharinae clade with high support values. Hence, these findings strongly indicate the presence of a new species in the S. catharinae clade from the southwestern portion of the Brazilian savannah. To be properly validated as a novel species, detailed comparative morphological and bioacustic studies with other taxa from Brazil such asS. canastrensis, S. centralis, S. luizotavioi, S. machadoi, S. pombali and S. skaios are required.     

Monograph of the Afrotropical species of Scelio Latreille (Hymenoptera,Platygastridae), egg parasitoids of acridid grasshoppers (Orthoptera,Acrididae)

The genus Scelio is a cosmopolitan and speciose group of solitary parasitoids of the eggs of short-horned grasshoppers (Orthoptera: Acrididae). A number of these hosts are important pests, including plague locusts of the genus Schistocerca. Species of Scelio are recognized as potentially important biological control agents, but this possibility has yet to be fully realized, in part because the species-level taxonomy is still incompletely developed. The species of the pulchripennis group have been recently revised. As a continuation of this effort, here we revise the Afrotropical species of Scelio, excluding the pulchripennis species group. Sixty two (62) species are treated, 48 of which are new. Species are classified into the following species groups: ernstii (12 species, 9 new), howardi (23 species, 19 new), ipomeae (6 species, 5 new), irwini (4 species, 3 new), simoni (3 new species) and walkeri (12 species, 9 new). Keys to species groups and to the species within each group are provided. New species described are: S. albatus Yoder, sp. n., S. aphares Yoder, sp. n., S. apospastos Yoder, sp. n., S. ardelio Yoder, sp. n., S. aurantium Yoder, sp. n., S. balo Valerio & Yoder, sp. n., S. bayanga Yoder, sp. n., S. bubulo Yoder, sp. n., S. cano Yoder, sp. n., S. clypeatus Yoder, sp. n., S. concavus Yoder, sp. n., S. copelandi Yoder, sp. n., S. crepo Yoder, sp. n., S. destico Yoder, sp. n., S. dupondi Yoder, sp. n., S. effervesco Yoder, sp. n., S. erugatus Yoder, sp. n., S. exophthalmus Yoder, sp. n., S. fremo Valerio & Yoder, sp. n., S. gemo Yoder, sp. n., S. grunnio Yoder, sp. n., S. harinhalai Yoder, sp. n., S. igland Yoder, sp. n., S. impostor Yoder, sp. n., S. irwini Yoder, sp. n., S. janseni Yoder, sp. n., S. latro Yoder, sp. n., S. memorabilis Yoder, sp. n., S. modulus Yoder, sp. n., S. mutio Yoder, sp. n., S. ntchisii Yoder, sp. n., S. parkeri Yoder, sp. n., S. phaeoprora Yoder, sp. n., S. pilosilatus Yoder, sp. n., S. pipilo Yoder, sp. n., S. quasiclypeatus Yoder, sp. n., S. retifrons Yoder, sp. n., S. ructo Yoder, sp. n., S. scomma Yoder, sp. n., S. simoni Yoder, sp. n., S. simonolus Yoder, sp. n., S. somaliensis Yoder, sp. n., S. susurro Yoder, sp. n., S. tono Yoder, sp. n., S. transtrum Yoder, sp. n., S. tritus Yoder, sp. n., S. ululo Yoder, sp. n., S. vannoorti Valerio & Yoder, sp. n. The following species are redescribed: S. afer Kieffer, S. chapmani Nixon, S. howardi Crawford, S. ipomeae Risbec, stat. n., S. mauritanicus Risbec, S. philippinensis Ashmead, S. remaudierei Ferrière, S. striatus Priesner,S. taylori Nixon, and S. zolotarevskyi Ferrière. The genus Lepidoscelio Kieffer is treated as a junior synonym of Scelio Latreille, syn. n.; its type species, Lepidoscelio fuscipennis Kieffer, 1905 is transferred to Scelio, renamed Scelio obscuripennis Johnson, nom. n. (preoccupied by Scelio fuscipennis Ashmead, 1887), and redescribed. The following additional species are transferred from Lepidoscelio to Scelio: S. cayennensis (Risbec), comb. n., S. insularis Ashmead, rev. comb., S. luteus (Cameron), comb. n., S. thoracicus Ashmead, rev. comb. Lectotypes are designated for S. africanus Risbec, S. ipomeae Risbec, S. mauritanicus Risbec, S. remaudierei Ferrière, S. sudanensis Ferrière, and S. zolotarevskyi Ferrière. Scelio gaudens Nixon is a junior synonym of Scelio striatus Priesner, syn. n.; Scelio africanus Risbec and Scelio clarus Fouts are both junior synonyms of Scelio afer Kieffer, syn. n.; Scelio sudanensis Ferrière and Scelio cheops Nixon are both junior synonyms of Scelio zolotarevskyi Ferrière, syn. n.; Scelio cahirensis Priesner is a junior synonym of Scelio mauritanicus Risbec, syn. n. The name Scelio chapmanni Nixon is an incorrect original spelling, requiring an emendation to S. chapmani. Digital versions of the identification keys are available at http://www.waspweb.org/Platygastroidea/Keys/index.htm     

New insights into pollen morphology and its implications in the phylogeny of Sanguisorba L. (Rosaceae; Sanguisorbeae)

Pollen morphology of 13 species of the genus Sanguisorba (Rosaceae) was examined by light and scanning electron microscopy. The pollen morphology divided the genus into two main groups: (A) tricolporate with tapered colpus tips, and (B) either tricolporate with opened colpus tip or hexacolporate. The former group was further subdivided into those without vestibulum (A1: S.?alpina, S.?dodecandra, and S.?filiformis) and those with vestibulum (A2: S.?agrimonoides, S.?ancestroides, S.?annua, S.?cretica, S.?minor, and S.?verrucosa), whereas the latter group was subdivided into those with colpus narrow and similar to the A1 type (B1: S.?canadensis and S.?diandra), those with colpus and mesocolpus somewhat equally wide and forming hexacolporate aperture (B3: S.?albiflora, S.?armena, S.?media, S.?menziesii, S.?parviflora, S.?stipulata, and S.?tenuifolia), and those with colpus intermediate between the B1 and B3 types (B2: S.?hakusanensis, S.?microcephala, S.?obtusa, S.?officinalis, S.?polygama, and S.?sitchensis). It is suggested that the A1 type aperture would have evolved to the A2 type as a specialized form and the B types (B1 to B3) in a direction in which the hexacolporate aperture was derived. Implications of pollen morphology for infrageneric classification of Sanguisorba are discussed and the results are compared with molecular phylogenetic studies.     

The genus Scaphidium Olivier in East China (Coleoptera,Staphylinidae, Scaphidiinae)

A review of 21 species of Scaphidium Olivier from East China is presented, including 6 new species: S. jinmingi sp. n. (Zhejiang, Anhui, Chongqing), S. crypticum sp. n. (Zhejiang, Fujian, Jiangxi, Guangxi), S. varifasciatum sp. n. (Zhejiang, An’hui), S. robustum sp. n. (Fujian, Guizhou, Chongqing, Guangxi, Yunnan), S. connexum sp. n. (Zhejiang, Fujian, Guangxi), and S. bayibini sp. n. (An’hui). New province records for S. comes Löbl, S. grande Gestro, S. sauteri Miwa & Mitono, S. formosanum Pic, S. carinense Achard, S. sinense Pic, S. delatouchei Achard, S. biwenxuani He, Tang & Li, S. klapperichi Pic, S. stigmatinotum Löbl, S. wuyongxiangi He, Tang & Li, and S. direptum Tang & Li as well as some biological notes are reported. Habitus and diagnostic characters of all species are photographed and a key to Scaphidium species of East China is provided.     

Mitochondrial Genome of Spirometra theileri Compared with Other Spirometra Species

This study was carried out to provide information on the taxonomic classification and analysis of mitochondrial genomes of Spirometra theileri. One strobila of S. theileri was collected from the intestine of an African leopard (Panthera pardus) in the Maswa Game Reserve, Tanzania. The complete mtDNA sequence of S. theileri was 13,685 bp encoding 36 genes including 12 protein genes, 22 tRNAs and 2 rRNAs with absence of atp8. Divergences of 12 protein-coding genes were as follow: 14.9% between S. theileri and S. erinaceieuropaei, 14.7% between S. theileri and S. decipiens, and 14.5% between S. theileri with S. ranarum. Divergences of 12 proteins of S. theileri and S. erinaceieuropaei ranged from 2.3% in cox1 to 15.7% in nad5, while S. theileri varied from S. decipiens and S. ranarum by 1.3% in cox1 to 15.7% in nad3. Phylogenetic relationship of S. theileri with eucestodes inferred using the maximum likelihood and Bayesian inferences exhibited identical tree topologies. A clade composed of S. decipiens and S. ranarum formed a sister species to S. erinaceieuropaei, and S. theileri formed a sister species to all species in this clade. Within the diphyllobothridean clade, Dibothriocephalus, Diphyllobothrium and Spirometra formed a monophyletic group, and sister genera were well supported.     

Quantitative real time PCR assays for the enumeration of Saccharomyces cerevisiae and the Saccharomyces sensu stricto complex in human feces

There have been an increasing number of reports of yeast systemic infection involving Saccharomyces cerevisiae strains. The development of a rapid and reliable diagnostic tool is therefore warranted in order to explore the distribution of S. cerevisiae as an opportunistic pathogen in humans. In this study, we designed and validated five primer sets targeting the 26S rRNA gene of S. cerevisiae and the S. sensu stricto complex using 26 yeast strains. Among them, two sets of primers specifically amplified the 26S rRNA gene and the ITS region of S. cerevisiae strains, and three sets were specific for amplifying the same genes in the S. sensu stricto complex. After determining the optimal conditions of two primer pairs for quantitative real time PCR, human fecal samples were analyzed to examine the distribution of S. cerevisiae and the S. sensu stricto complex. It was possible to detect a single cell of S. cerevisiae in environmental sample. Qualitative PCR revealed that out of eleven fecal samples tested, one sample contained S. cerevisiae and four samples contained the S. sensu stricto complex. Quantitative real time PCR revealed that the target gene copy numbers of S. cerevisiae and the S. sensu stricto complex were 0.84 and 2.44 respectively, in 1 ng of DNA from the bulk fecal community.     

Penicillin-binding proteins and cell wall composition in beta-lactam-sensitive and -resistant strains of Staphylococcus sciuri

A close homologue of the acquired Staphylococcus aureus mecA gene is present as a native gene in Staphylococcus sciuri. We determined the patterns of penicillin-binding proteins (PBPs) and the peptidoglycan compositions of several S. sciuri strains to explore the functions of this mecA homologue, named pbpD, in its native S. sciuri environment. The protein product of pbpD was identified as PBP4 with a molecular mass of 84 kDa, one of the six PBPs present in representatives of each of three subspecies of S. sciuri examined. PBP4 had a low affinity for nafcillin, reacted with a monoclonal antibody raised against S. aureus PBP2A, and was greatly overproduced in oxacillin-resistant clinical isolate S. sciuri SS37 and to a lesser extent in resistant laboratory mutant K1M200. An additional PBP inducible by oxacillin and corresponding to S. aureus PBP2A was identified in another oxacillin-resistant clinical isolate, S. sciuri K3, which harbors an S. aureus copy of mecA. Oxacillin resistance depended on the overtranscribed S. sciuri pbpD gene in strains SS37 and K1M200, while the resistance of strain K3 depended on the S. aureus copy of mecA. Our data provide evidence that both S. aureus mecA and S. sciuri pbpD can function as resistance determinants in either an S. aureus or an S. sciuri background and that the protein products of these genes, S. aureus PBP2A and S. sciuri PBP4, can participate in the biosynthesis of peptidoglycan, the muropeptide composition of which depends on the bacterium “hosting” the resistance gene.     

Anthocyanins in Salix species: A new anthocyanin in salix purpurea bark

Cyanidin 3-glucoside and delphinidin 3-glucoside (minor component) occurred in the bark of Salix purpurea (29 cultivars examined), S. fragilis (3 cvs), S. americana (4 cvs), S. rubra (1 cv.), S. incana (1 cv.), S. aegyptica (1 cv.) and S. alba (3 cvs) and several hybrids. A previously unrecorded anthocyanin was also present in appreciable amounts in the bark of eleven S. purpurea cultivars, notably those with small leaves. In other large-leaved cultivars of S. purpurea (18) it occurred only in traces or was not detected with certainty. A trace was found in one purpurea hybrid, but it was not detected in four others. Small amounts of the new anthocyanin were also found in S. incana (1 cv.), S. fragilis cv. Basfordiana, S. americana cv. Cordata and one hybrid, but were absent from other cultivars of S. fragilis (2) and S. americana (2), and also from S. alba (3), S. aegyptica (1), S. daphnoides (1), S. rubra (1), S. triandra (1), S. viminalis (1) and three hybrids. The new anthocyanin is unique in containing fructose as well as glucose and is based upon a previously undescribed anthocyanidin, possibly dimeric in nature, which is provisionally named purpurinidin.     

Nontyphoidal Salmonellae in United Kingdom Badgers: Prevalence and Spatial Distribution

Eighteen (72%) of 25 badger social groups were found to excrete Salmonella enterica serovar Ried, S. enterica serovar Binza, S. enterica serovar Agama, or S. enterica serovar Lomita. Each serovar was susceptible to a panel of antimicrobials. Based on results of pulsed-field gel electrophoresis, the S. enterica serovar Agama and S. enterica serovar Binza isolates were very similar, but two clones each of S. enterica serovar Lomita and S. enterica serovar Ried were found. Badgers excreting S. enterica serovar Agama were spatially clustered.     

Deoxyribonucleic Acid Homology Among Lactic Streptococci

A comparison was made by deoxyribonucleic acid homology of 45 strains of lactic streptococci, using two strains of Streptococcus cremoris and three strains of Streptococcus lactis as reference strains. All S. cremoris strains were grouped together by deoxyribonucleic acid homology. S. lactis strains formed a second group, except that three strains of S. lactis showed a high degree of homology with S. cremoris strains. The three Streptococcus diacetylactis strains could not be differentiated from S. lactis strains. In spite of these differences between S. lactis and S. cremoris strains, the majority of S. cremoris, S. lactis, and S. diacetylactis strains studied had at least 50% of their base sequences in common. In contrast, Streptococcus thermophilus strains generally showed little relationship with the other strains of lactic streptococci. The relevance of these findings to the selection of starter strains for cheese making is discussed.     

Characterization of Streptomyces isolates causing colour changes of mural paintings in ancient Egyptian tombs

Paintings in ancient Egyptian tombs often suffer colour changes due to microbial growth and colonization. Streptomyces strains were isolated from mural paintings of Tell Basta and Tanis tombs (East of Nile Delta, Egypt) and were identified using biochemical and molecular methods. The16S rDNA sequences data indicated that isolated strains were closely related to S. coelicolor, S. albidofuscus, S. ambofaciens, S. canarius, S. parvullus, S. corchorusii, S. albidofuscus and S. nigrifaciens. It could be shown that Streptomyces strains are involved on a large scale in the colour changes of paintings and stone support by producing a wide range of metabolites such as acids (oxalic, citric and sulphuric acids), biopigments of melanin, carotenoids, and hydrogen sulphide.