Temporal Allocation of Foraging Effort in Female Australian Fur Seals (Arctocephalus pusillus doriferus)

Across an individual''s life, foraging decisions will be affected by multiple intrinsic and extrinsic drivers that act at differing timescales. This study aimed to assess how female Australian fur seals allocated foraging effort and the behavioural changes used to achieve this at three temporal scales: within a day, across a foraging trip and across the final six months of the lactation period. Foraging effort peaked during daylight hours (57% of time diving) with lulls in activity just prior to and after daylight. Dive duration reduced across the day (196 s to 168 s) but this was compensated for by an increase in the vertical travel rate (1500–1600 m·h⁻¹) and a reduction in postdive duration (111–90 s). This suggests physiological constraints (digestive costs) or prey availability may be limiting mean dive durations as a day progresses. During short trips (<2.9 d), effort remained steady at 55% of time diving, whereas, on long trips (>2.9 d) effort increased up to 2–3 d and then decreased. Dive duration decreased at the same rate in short and long trips, respectively, before stabilising (long trips) between 4–5 d. Suggesting that the same processes (digestive costs or prey availability) working at the daily scale may also be present across a trip. Across the lactation period, foraging effort, dive duration and vertical travel rate increased until August, before beginning to decrease. This suggests that as the nutritional demands of the suckling pup and developing foetus increase, female effort increases to accommodate this, providing insight into the potential constraints of maternal investment in this species.     

Stable Isotope Models Predict Foraging Habitat of Northern Fur Seals (Callorhinus ursinus) in Alaska

We developed models to predict foraging habitat of adult female northern fur seals (Callorhinus ursinus) using stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values from plasma and red blood cells. Binomial generalized linear mixed models were developed using blood isotope samples collected from 35 adult female fur seals on three breeding colonies in Alaska during July-October 2006. Satellite location and dive data were used to define habitat use in terms of the proportion of time spent or dives made in different oceanographic/bathymetric domains. For both plasma and red blood cells, the models accurately predicted habitat use for animals that foraged exclusively off or on the continental shelf. The models did not perform as well in predicting habitat use for animals that foraged in both on- and off-shelf habitat; however, sample sizes for these animals were small. Concurrently collected scat, fatty acid, and dive data confirmed that the foraging differences predicted by isotopes were associated with diet differences. Stable isotope samples, dive data, and GPS location data collected from an additional 15 females during August-October 2008 validated the effective use of the models across years. Little within year variation in habitat use was indicated from the comparison between stable isotope values from plasma (representing 1-2 weeks) and red blood cells (representing the prior few months). Constructing predictive models using stable isotopes provides an effective means to assess habitat use at the population level, is inexpensive, and can be applied to other marine predators.     

Foraging-Based Enrichment Promotes More Varied Behaviour in Captive Australian Fur Seals (Arctocephalus pusillus doriferus)

During wild foraging, Australian fur seals (Arctocephalus pusillus doriferus) encounter many different types of prey in a wide range of scenarios, yet in captive environments they are typically provided with a narrower range of opportunities to display their full repertoire of behaviours. This study aimed to quantitatively explore the effect of foraging-based enrichment on the behaviour and activity patterns displayed by two captive Australian fur seals at Melbourne Zoo, Australia. Food was presented as a scatter in open water, in a free-floating ball device, or in a static box device, with each treatment separated by control trials with no enrichment. Both subjects spent more time interacting with the ball and static box devices than the scatter feed. The total time spent pattern swimming was reduced in the enrichment treatments compared to the controls, while the time spent performing random swimming behaviours increased. There was also a significant increase in the total number of bouts of behaviour performed in all three enrichment treatments compared to controls. Each enrichment method also promoted a different suit of foraging behaviours. Hence, rather than choosing one method, the most effective way to increase the diversity of foraging behaviours, while also increasing variation in general activity patterns, is to provide seals with a wide range of foraging scenarios where food is encountered in different ways.     

Identification of Prey Captures in Australian Fur Seals (Arctocephalus pusillus doriferus) Using Head-Mounted Accelerometers: Field Validation with Animal-Borne Video Cameras

This study investigated prey captures in free-ranging adult female Australian fur seals (Arctocephalus pusillus doriferus) using head-mounted 3-axis accelerometers and animal-borne video cameras. Acceleration data was used to identify individual attempted prey captures (APC), and video data were used to independently verify APC and prey types. Results demonstrated that head-mounted accelerometers could detect individual APC but were unable to distinguish among prey types (fish, cephalopod, stingray) or between successful captures and unsuccessful capture attempts. Mean detection rate (true positive rate) on individual animals in the testing subset ranged from 67-100%, and mean detection on the testing subset averaged across 4 animals ranged from 82-97%. Mean False positive (FP) rate ranged from 15-67% individually in the testing subset, and 26-59% averaged across 4 animals. Surge and sway had significantly greater detection rates, but also conversely greater FP rates compared to heave. Video data also indicated that some head movements recorded by the accelerometers were unrelated to APC and that a peak in acceleration variance did not always equate to an individual prey item. The results of the present study indicate that head-mounted accelerometers provide a complementary tool for investigating foraging behaviour in pinnipeds, but that detection and FP correction factors need to be applied for reliable field application.     

Habitat Use by Weddell Seals and Emperor Penguins Foraging in the Ross Sea, Antarctica

The only apex predators that live year-round at high latitudesof the Ross Sea are the Weddell seal and emperor penguin. Theseasonal distribution, foraging depths, and diet of these twospecies appear to overlap. What makes it possible for emperorpenguins and Weddell seals to co-exist at high latitude throughoutthe winter when other marine tetrapods apparently cannot? Bothspecies have similar adaptations for exploitation of the deep-waterhabitat, forage on the same species, and routinely make longand deep dives. Yet, despite these similarities, there is probablylittle trophic overlap between the adults of both species dueto geographical and seasonal differences in habitat use. Forexample, during the winter months while female emperor penguinsare ranging widely in the pack ice, adult seals are foragingand fattening for the upcoming summer fast, literally beneaththe feet of the male penguins. However, there is more extensiveoverlap between juvenile seals and adult penguins, and shiftsin prey abundance and/or distribution would likely affect thesetwo groups similarly. In contrast, juvenile penguins appearto avoid inter- and intra- specific competition by leaving theRoss Sea once they molt.     

Foraging by Male and Female Solitary Bees with Implications for Pollination

Both male and female solitary bees visit flowers for rewards. Sex related differences in foraging efficiency may also affect their probability to act as pollinators. In some major genera of solitary bees, males can be identified from a distance enabling a comparative foraging-behavior study. We have simultaneously examined nectar foraging of males and females of three bee species on five plant species in northern Israel. Males and females harvested equal nectar amounts but males spent less time in each flower increasing their foraging efficiency at this scale. The overall average visit frequencies of females and males was 27.2 and 21.6 visits per flower per minute respectively. Females flew shorter distances increasing their visit frequency, relative foraging efficiency and their probability to pollinate. The proportion of conspecific pollen was higher on females, indicating higher floral constancy and pollination probability. The longer flights of males increase their probability to cross-pollinate. Our results indicate that female solitary bees are more efficient foragers; females seem also to be more efficient pollinators but males contribute more to long-distance pollen flow.     

Utilisation of nutrients by embryos of the enigmatic Australian viviparous skink Niveoscincus coventryi

The Eugongylus species group of Australian lygosomine skinks provides an unparalleled opportunity to study the evolution of placentotrophy. Viviparity and placentotrophy have evolved in two lineages, currently recognised as the genera Pseudemoia and Niveoscincus. The genus Niveoscincus is important because it is the only lineage of squamates in which variation in placental morphology and in the pattern of embryonic nutrition is known. Niveoscincus coventryi has the least complex placental morphology among species currently assigned to the genus. We quantified the net uptake of nutrients across the placenta of N. coventryi for comparison with other species in the genus and with other viviparous and oviparous lizards. The pattern of embryonic nutrition of N. coventryi is similar to other viviparous lizards with simple placentae in that there is no net uptake of dry matter during development but there is a net uptake of water, calcium, potassium, and sodium. There is no net uptake of lipid, nitrogen (an index of protein), or magnesium. We conclude that N. coventryi is predominantly lecithotrophic. Further, if N. coventryi is the sister taxon to Tasmanian Niveoscincus, then the distribution of patterns of embryonic nutrition among members of this clade suggests that the evolution of placentotrophy occurred during radiation of this lineage in Tasmania.     

Foraging Behaviour and Landscape Utilisation by the Endangered Golden-Crowned Flying Fox (Acerodon jubatus), The Philippines

Species of Old World fruit-bats (family Pteropodidae) have been identified as the natural hosts of a number of novel and highly pathogenic viruses threatening livestock and human health. We used GPS data loggers to record the nocturnal foraging movements of Acerodon jubatus, the Golden-crowned flying fox in the Philippines to better understand the landscape utilisation of this iconic species, with the dual objectives of pre-empting disease emergence and supporting conservation management. Data loggers were deployed on eight of 54 A. jubatus (two males and six females) captured near Subic Bay on the Philippine island of Luzon between 22 November and 2 December 2010. Bodyweight ranged from 730 g to 1002 g, translating to a weight burden of 3–4% of bodyweight. Six of the eight loggers yielded useful data over 2–10 days, showing variability in the nature and range of individual bat movements. The majority of foraging locations were in closed forest and most were remote from evident human activity. Forty-six discrete foraging locations and five previously unrecorded roost locations were identified. Our findings indicate that foraging is not a random event, with the majority of bats exhibiting repetitious foraging movements night-to-night, that apparently intact forest provides the primary foraging resource, and that known roost locations substantially underestimate the true number (and location) of roosts. Our initial findings support policy and decision-making across perspectives including landscape management, species conservation, and potentially disease emergence.     

Utilisation of carbon substrates by orchid and ericoid mycorrhizal fungi from Australian dry sclerophyll forests

The utilisation of a range of cell-wall-related and aromatic carbon substrates by multiple genotypes of three ericoid mycorrhizal fungal taxa was compared with two orchid mycorrhizal fungal taxa. Both groups of fungi catabolised most common substrates, though significant inter- and intraspecific variability was observed in the use of a few carbon substrates. Orchid mycorrhizal fungi had limited access to tannic acid as a carbon source and did not use phenylalanine, while the ericoid mycorrhizal fungi used both. Utilisation of tryptophan was limited to single genotypes of each of the orchid mycorrhizal fungi, and to only two of the three ericoid mycorrhizal fungi examined. Although broadly similar, some significant differences apparently exist in carbon catabolism of ericoid and orchid mycorrhizal fungi from the same habitat. Functional and ecological implications of these observations are discussed.     

Utilisation of carbon substrates by multiple genotypes of ericoid mycorrhizal fungal endophytes from eastern Australian Ericaceae

The abilities of six genotypes of two putative Helotiales ascomycete ericoid mycorrhizal fungal taxa from Woollsia pungens and Leucopogon parviflorus (Ericaceae) to utilise glucose, galactose, mannose, cellobiose, carboxymethylcellulose, crystalline cellulose, starch and xylan as sole carbon sources were tested in axenic liquid culture. With the exception of all taxon II isolates on carboxymethylcellulose, all genotypes of both taxa produced measurable biomass on all substrates. Significant intraspecific variation was observed in biomass production on all substrates. While pooled data for all genotypes of each taxon revealed significant interspecific differences in biomass production on carboxymethylcellulose, glucose, cellobiose, and starch, mean biomass production for each taxon on the latter three substrates differed less than threefold, suggesting that the saprotrophic abilities of the two taxa are broadly similar.     

Accelerometers Identify New Behaviors and Show Little Difference in the Activity Budgets of Lactating Northern Fur Seals (Callorhinus ursinus) between Breeding Islands and Foraging Habitats in the Eastern Bering Sea

We tagged 82 lactating northern fur seals (Callorhinus ursinus) with tri-axial accelerometers and magnetometers on two eastern Bering Sea islands (Bogoslof and St. Paul) with contrasting population trajectories. Using depth data, accelerometer data and spectral analysis we classified time spent diving (30%), resting (~7%), shaking and grooming their pelage (9%), swimming in the prone position (~10%) and two types of previously undocumented rolling behavior (29%), with the remaining time (~15%) unspecified. The reason for the extensive rolling behavior is not known. We ground-truthed the accelerometry signals for shaking and grooming and rolling behaviors—and identified the acceleration signal for porpoising—by filming tagged northern fur seals in captivity. Speeds from GPS interpolated data indicated that animals traveled fastest while in the prone position, suggesting that this behavior is indicative of destination-based swimming. Very little difference was found in the percentages of time spent in the categorical behaviors with respect to breeding islands (Bogoslof or St. Paul Island), forager type (cathemeral or nocturnal), and the region where the animals foraged (primarily on-shelf <200m, or off-shelf > 200m). The lack of significant differences between islands, regions and forager type may indicate that behaviors summarized over a trip are somewhat hardwired even though foraging trip length and when and where animals dive are known to vary with island, forager type and region.     

Fortuitous Encounters between Seagliders and Adult Female Northern Fur Seals (Callorhinus ursinus) off the Washington (USA) Coast: Upper Ocean Variability and Links to Top Predator Behavior

Behavioral responses by top marine predators to oceanographic features such as eddies, river plumes, storms, and coastal topography suggest that biophysical interactions in these zones affect predators'' prey, foraging behaviors, and potentially fitness. However, examining these pathways is challenged by the obstacles inherent in obtaining simultaneous observations of surface and subsurface environmental fields and predator behavior. In this study, migratory movements and, in some cases, diving behavior of 40 adult female northern fur seals (NFS; Callorhinus ursinus) were quantified across their range and compared to remotely-sensed environmental data in the Gulf of Alaska and California Current ecosystems, with a particular focus off the coast of Washington State (USA) – a known foraging ground for adult female NFS and where autonomous glider sampling allowed opportunistic comparison of seal behavior to subsurface biophysical measurements. The results show that in these ecosystems, adult female habitat utilization was concentrated near prominent coastal topographic, riverine, or inlet features and within 200 km of the continental shelf break. Seal dive depths, in most ecosystems, were moderated by surface light level (solar or lunar), mirroring known behaviors of diel vertically-migrating prey. However, seal dives differed in the California Current ecosystem due to a shift to more daytime diving concentrated at or below the surface mixed layer base. Seal movement models indicate behavioral responses to season, ecosystem, and surface wind speeds; individuals also responded to mesoscale eddies, jets, and the Columbia River plume. Foraging within small scale surface features is consistent with utilization of the inner coastal transition zone and habitats near coastal capes, which are known eddy and filament generation sites. These results contribute to our knowledge of NFS migratory patterns by demonstrating surface and subsurface behavioral responses to a spatially and temporally dynamic ocean environment, thus reflecting its influence on associated NFS prey species.     

Recognition of DNA by Fur: a reinterpretation of the Fur box consensus sequence

Ferric uptake repressor (Fur) proteins regulate the expression of iron homeostasis genes in response to intracellular iron levels. In general, Fur proteins bind with high affinity to a 19-bp inverted repeat sequence known as the Fur box. An alignment of 19 operator sites recognized by Bacillus subtilis Fur revealed a different conserved 15-bp (7-1-7) inverted repeat present twice within this 19-bp consensus sequence. We demonstrated using electrophoretic mobility shift assays that this 7-1-7 inverted repeat comprises a minimal recognition site for high-affinity binding by Fur. The resulting revised consensus sequence is remarkably similar to a related 7-1-7 inverted repeat sequence recognized by PerR, a Fur paralog. Our analysis of the affinity and stoichiometry of DNA binding by B. subtilis Fur, together with a reinterpretation of previously described studies of Escherichia coli Fur, supports a model in which the 19-bp Fur box represents overlapping recognition sites for two Fur dimers bound to opposite faces of the DNA helix. The resulting recognition complex is reminiscent of that observed for the functionally related protein DtxR. Like Fur, DtxR contains a helix-turn-helix DNA-binding motif, recognizes a 19-bp inverted repeat sequence, and has a typical DNase I footprint of approximately 30 bp. By envisioning a similar mode of DNA recognition for Fur, we can account for the internal symmetries noted previously within the Fur box, the tendency of Fur to extend into adjacent regions of DNA in a sequence-selective manner, and the observed patterns of DNA protection against enzymatic and chemical probes.     

Isolation and Characterization of Campylobacter spp. from Antarctic Fur Seals (Arctocephalus gazella) at Deception Island,Antarctica

The presence of Campylobacter spp. was investigated in 41 Antarctic fur seals (Arctocephalus gazella) and 9 Weddell seals (Leptonychotes weddellii) at Deception Island, Antarctica. Infections were encountered in six Antarctic fur seals. The isolates, the first reported from marine mammals in the Antarctic region, were identified as Campylobacter insulaenigrae and Campylobacter lari.The Antarctic and sub-Antarctic regions are often regarded as pristine landscapes, unaffected by human activity. A limited number of surveys have been carried out to investigate the possible occurrence of zoonotic enteropathogens and if certain bacteria could be used as tools for evaluating biological pollution in this area (4, 11). In the case of Campylobacter species, there have been only three reports in the literature, but in all of them Campylobacter was isolated from marine seabirds but not from marine mammals. Campylobacter jejuni was isolated in Antarctic and sub-Antarctic areas from Macaroni penguins (Eudyptes chrysolophus) (4), and Campylobacter lari was isolated from Brown skuas, South Polar skuas, and Adelie penguins (2, 11).Reports of Campylobacter species isolated from marine mammals are rare. Campylobacter insulaenigrae was isolated from three harbor seals (Phoca vitulina) and a harbor porpoise (Phocoena phocoena) in Scotland (7). The isolation of C. jejuni, C. lari, and an unknown Campylobacter species from juvenile northern elephant seals (Mirounga angustirostris) in California was also reported (22). Finally, 71 isolates of C. insulaenigrae and 1 isolate similar to but distinct from both Campylobacter upsaliensis and Campylobacter helveticus were isolated from northern elephant seals in California (23). In the South Georgia Archipelago, fecal swabs were taken from 206 Antarctic fur seal pups, but no isolates could be obtained (4). In this study, we successfully isolated C. lari from 7.3% of Antarctic fur seals (Arctocephalus gazella) sampled and C. insulaenigrae from a further 7.3%. On the other hand, Campylobacter was not detected in the nine Weddell seals (Leptonychotes weddellii) sampled. To our knowledge, this is the first report on the isolation of C. lari and C. insulaenigrae from marine mammals in the Antarctic region.Fieldwork was conducted at Deception Island (latitude of 62°58′S and longitude of 60°40′W), in the South Shetland Islands. During January to February 2007, Antarctic fur seals (Arctocephalus gazella) and Weddell seals (Leptonychotes weddellii) were captured and fecal samples were collected by insertion of sterile cotton wool swabs into the rectum of the marine mammals. A total of 41 Antarctic fur seals and 9 Weddell seals were sampled. The distribution by ages was of 7 adults (over 4 years of age with breeding activity), 19 subadults (2 to 4 years of age), and 15 juvenile Antarctic fur seals (less than 2 years of age), and 8 adult Weddell seals and 1 juvenile. All animals presented a good body condition and showed no symptoms at the time of sampling.Three swabs were taken from each animal and were placed in FBP medium (8) with 0.5% active charcoal (Sigma Ltd.), Amies transport medium with charcoal, and Cary Blair transport medium, respectively. All samples were kept at +4 to 8°C until culture in the lab. The number of days between sampling and cultivation varied from 96 to 124 days, with a median value of 105 days.Each swab was placed in 10 ml of Campylobacter enrichment broth (Lab M) with 5% laked horse blood and CAT supplement (cefoperazone [8 μg/ml], teicoplanin [4 μg/ml], and amphotericin B [10 μg/ml]) at 37°C. The broth was incubated at 37°C for 48 h and 5 days in 3.5-liter anaerobic containers using CampyGen sachets (Oxoid), before an aliquot of 100 μl was plated onto CAT agar and the plates were incubated at 37°C for 72 h in a microaerobic atmosphere. In addition, a 47-mm-diameter cellulose membrane with 0.60-μm pores was placed on the surface of an anaerobe agar base (Oxoid) with 5% laked horse blood. Eight to 10 drops of enrichment broth (200 μl) were placed onto the surface of the membrane. The membrane was left for 20 to 30 min on the agar surface at room temperature until all of the fluid had passed through (20). The plates were incubated as described above, but for 5 days to isolate the less common, slower growing species.Isolates were examined by dark-field microscopy to determine morphology and motility and tested to determine whether oxidase was produced. For each sample, five isolates from each of the solid media that had typical morphology and motility and for which the oxidase test was positive were frozen at −80°C in FBP medium (8) until they were tested by phenotypic and genotypic methods.Original Campylobacter identification was done by Gram staining, catalase activity, hippurate hydrolysis, ability to hydrolyze indoxyl acetate, urease activity, H₂S production on triple-sugar iron slants, growth at 25°C and 42°C in a microaerophilc environment, growth at 37°C in an aerobic atmosphere, and agglutination with Microscreen latex (Microgen, Camberley, United Kingdom).No differences between the strains were observed in any of the phenotypic tests used. All isolates showed a Gram-negative, slender, curved, seagull wing-like morphology under light microscopy and positive reactions in the catalase test. They were negative for hippurate and indoxyl acetate hydrolysis and urease and did not show H₂S production. In addition, they grew at 42°C but did not grow at 25°C or 37°C in an aerobic atmosphere. Finally, all of them were positive in the agglutination test.Because phenotypic results commonly lead to misidentification of Campylobacter species, it is recommended that a molecular method be included in the identification scheme for Campylobacter (5, 15). Identification of the isolates was performed using 16S rRNA gene PCR and sequence analysis (15, 21). Forward and reverse conserved 16S rRNA eubacterial primers 8F (5′-AGAGTTTGATCCTGGCTCAG-3′) and 1492R (5′-GGTTACCTTGTTACGACTT-3′) were used to amplify the 16S rRNA according to the protocol described by Jang et al. (9). Forward and reverse sequencing reactions were performed by the Laboratorio Central de Veterinaria''s DNA sequencing facility (LCV Algete, Madrid, Spain). Three strains were identified as C. lari and the other three as C. insulaenigrae based on both forward and reverse sequence analysis.Molecular characterization of strains was carried out using a combination of pulsed-field gel electrophoresis (PFGE) using KpnI enzyme and multilocus sequence typing (MLST). Preparation of intact Campylobacter DNA for PFGE was performed following the Pulsenet protocol (17, 24). PFGE for the restriction enzyme KpnI (Takara, Conda, Spain) was performed following the protocol described by Ribot et al. (17). DNA fragments were resolved on 0.9% Seakem Gold agarose gels (Iberlabo, Spain) with a Bio-Rad CHEF DRIII system (Bio-Rad, Spain) at 14°C and 6 V/cm. Electrophoresis was carried out for 22 h with pulse times ramping from 4 s to 20 s. The fingerprinting experiments were analyzed using the InfoQuest FP software (Bio-Rad, Spain), and the dendrogram was constructed using the unweighted-pair group method using average linkages (UPGMA).MLST of C. lari strains was performed as described by Miller et al. (13). In the case of C. insulaenigrae strains, MLST was performed following the protocol described by Stoddard et al. (23). All amplicons were sequenced by the Sequencing Service of the Instituto de Salud Carlos III (Madrid, Spain). Sequence data were collated, and alleles were assigned using the Campylobacter PubMLST database (http://pubmlst.org/campylobacter/). Novel alleles and sequence types were submitted for allele and sequence type (ST) designations when appropriate.Regarding the age distribution of animals, C. lari was isolated from 1 of 7 adult (14.3%), 1 of 19 subadult (5.3%), and 1 of 15 juvenile (6.6%) Antarctic fur seals. C. insulaenigrae was isolated from 1 of 7 adults (14.3%) and 2 of 19 of subadults (10.5%) but not from juvenile animals (Table ​(Table1).1). All strains were obtained from the swabs kept in FBP transport medium.

TABLE 1.

Source of Campylobacter isolates

Utilisation of structurally diverse organophosphonates by Streptomycetes

A group of streptomycete strains was found able to utilise a wide range of structurally diverse phosphonates as a sole phosphorus source. No relation could be observed between ability to synthesise compounds containing a direct carbon-to-phosphorus (C-P) bond and biodegradative potential towards phosphonates in the strains studied. Streptomyces morookaensis DSM 40565 could degrade 2-amino-4-phosphonobutyrate as a sole nitrogen and phosphorus source in a stereoselective-like manner. This result suggests the existence of a new metabolic pathway for C-P bond breakage.     

Utilisation of protein by human gut bacteria

Abstract Mixed populations of human gut bacteria degraded cas casein by producing a variety of cell-bound and extracellular proteolytic enzymes. Casein was initially hydrolysed to TCA soluble peptides which were subsequently broken down to volatile fatty acids, ammonia, dicarboxylic acids and a range of phenolic compounds. Amino acids did not accumulate to any extent during casein breakdown, suggesting that the rate of peptide hydrolysis was the limiting step in protein utilisation by these bacteria. Similar fermentation products were produced from bovine serum albumin, however, the insoluble protein collagen was considerably more resistant to degradation by the colonic microflora, as evidenced by the reduced quantities of fermentation end-products formed.